These are the RV-8/8A speeds recorded in SARL since 2007
This is not a perfect fit to your question but it does provide a lot of historical max speed data on RV-8s without altitude restrictions. The RV Red class has 320 cu. in. RV Blue Class is limited to 360 cu. in. and the RV Gold can have 390 cu. in. You will note that John Huft flew in the Blue and Gold Classes. It is the same airplane and engine (IO 360), he just felt sorry for the rest of us Blues and decided to take on the 390s in the Gold Class.
Bob Axsom
AirVenture Cup 2008 7/27/08 RV Blue RV-8 Huft, John 217.17 249.91
Rocket 100, 2010 11/20/10 RV Gold RV-8 Huft, John 205.39 236.36
AirVenture Cup 2007 7/23/07 RV Blue RV-8 Huft, John 204.56 235.40
AirVenture Cup 2008 7/27/08 RV Blue RV-8 Ross, Jon 202.59 233.14
AirVenture Cup 2010 7/26/10 RV Gold RV-8 Huft, John 201.97 232.42
Grace Flight 2009 10/4/09 RV Blue RV-8 Huft, John 201.71 232.12
Taylor 100 2009 3/16/09 RV Blue RV-8 Huft, John 201.29 231.64
AirVenture Cup 2008 7/27/08 Sport FX RV-8 Martin, Dick 202.28 231.63
Pagosa Springs 2010 9/26/10 RV Gold RV-8 Huft, John 200.93 231.07
Colorado 150, 2008 6/29/08 RV Blue RV-8 Huft, John 199.27 229.31
Pagosa Springs 100 2009 9/27/09 RV Blue RV-8 Huft, John 199.38 229.29
Rocket 100 2008 11/23/08 RV Blue RV-8 Huft, John 197.43 227.20
Texoma 100 4/25/10 RV Gold RV-8 Ogden, Deene 197.15 226.72
Rocket 100, 2010 11/20/10 RV Gold RV-8 Ogden, Deene 196.89 226.58
Memorial 130, Terrell, TX 5/28/11 RV Gold RV-8 Hajek, Jerry 196.00 225.55
Lone Star Air Rally 5/14/11 RV Gold RV-8 Hajek, Jerry 195.77 225.29
Rocket 100, 2010 11/20/10 RV Blue RV-8 Rovey, Jason 195.44 224.90
Rocket 100, 2007 11/18/07 RV Blue RV-8 Huft, John 194.78 224.15
Sulphur Springs 130 7/18/10 RV Gold RV-8 Ogden, Deene 194.59 223.94
Rocket 100, 2010 11/20/10 RV Gold RV-8 Hajek, Jerry 194.43 223.74
AirVenture Cup 2007 7/23/07 Sport FX RV-8 Martin, Dick 194.36 223.67
AirVenture Cup 2008 7/27/08 RV Blue RV-8 Carroll, Alan 193.76 222.97
Tennessee Valley Air Race 2010 10/30/10 RV Blue RV-8 Rovey, Jason 193.50 222.72
Memorial 130, Terrell, TX 5/28/11 RV Blue RV-8 Rovey, Jason 193.53 222.72
Texoma 100, 2008 4/20/08 RV Blue RV-8 Christman, Dave 192.88 222.00
Tennessee Valley Air Race 2010 10/30/10 RV Blue RV-8 Carroll, Alan 192.07 221.07
Texoma 100, 2011 4/16/11 RV Gold RV-8 Hajek, Jerry 192.17 221.07
AirVenture Cup 2007 7/23/07 RV Blue RV-8 Ross, Jon 192.04 221.00
AirVenture Cup 2007 7/23/07 RV Blue RV-8 Carroll, Alan 191.77 220.68
Big Sky Air Race 7/9/11 RV Blue RV-8 Rovey, Jason 191.31 220.15
Indy Air Race 8/13/11 RV Blue RV-8 Carroll, Alan 191.29 220.14
2011 West Tesas 100 6/18/11 RV Blue RV-8 Rovey, Jason 190.36 219.07
AirVenture Cup (TH) 2011 7/25/11 RV Gold RV-8 Ring, R. Damon 190.31 219.00
AirVenture Cup 2009 7/27/09 RV Blue RV-8 Huft, John 189.13 217.69
AirVenture Cup 2010 7/26/10 RV Blue RV-8 Ross, Jon 189.01 217.51
Taylor 100 2009 3/16/09 RV Blue RV-8 Carroll, Alan 188.96 217.46
Great Canadian Air Rally 2010 8/22/10 RV Blue RV-8 Carroll, Alan 188.83 217.30
Taylor 150 4/11/10 RV Gold RV-8 Ogden, Deene 188.69 217.14
Taylor 100 2009 3/16/09 RV Blue RV-8 Christman, Dave 188.33 216.73
Sulphur Springs 130 7/18/10 RV Blue RV-8 Rovey, Jason 188.12 216.48
West Texas 100 6/6/10 RV Gold RV-8 Huft, John 187.99 216.33
AirVenture Cup 2008 7/27/08 RV Blue RV-8 Schryver, Fred 187.49 215.76
Rocket 100, 2010 11/20/10 RV Blue RV-8 Grover, David 187.39 215.65
Texoma 100, 2011 4/16/11 RV Blue RV-8 Taylor, Craig 186.87 214.97
Pagosa Springs 2010 9/26/10 RV Blue RV-8 Rovey, Jason 186.47 214.45
Memorial 130, Terrell, TX 5/28/11 RV Blue RV-8 Taylor, Craig 186.31 214.41
AirVenture Cup (Matoon) 2011 7/24/11 RV Gold RV-8 Ring, R. Damon 186.05 214.11
Grace Flight 2010 10/2/10 RV Blue RV-8 Carroll, Alan 185.70 213.69
Grace Flight 2010 10/2/10 RV Blue RV-8 Rovey, Jason 185.32 213.25
Grace Flight 2010 10/2/10 RV Blue RV-8 Chrisman, Dave 184.94 212.81
Grace Flight 2010 10/2/10 RV Gold RV-8 Ogden, Deene 184.86 212.73
AirVenture Cup 2007 7/23/07 RV Blue RV-8 Jordan, Scott 184.85 212.72
AirVenture Cup 2007 7/23/07 RV Blue RV-8 Schryver, Fred 184.85 212.72
Pagosa Springs 2010 9/26/10 RV Blue RV-8 Taylor, Craig 183.31 210.81
AirVenture Cup 2010 7/26/10 RV Blue RV-8 Carroll, Alan 182.98 210.57
Colorado 150, 2008 6/29/08 RV Blue RV-8 Carroll, Alan 181.34 208.68
2011 West Tesas 100 6/18/11 RV Blue RV-8 Krebaum, Ken 180.69 207.93
Texoma 100 2009 5/31/09 RV Blue RV-8 Tuckey, Pat* 180.59 207.82
AirVenture Cup 2009 7/27/09 RV Blue RV-8 Ross, Jon 180.44 207.65
AirVenture Cup 2009 7/27/09 Sport FX RV-8 Martin, Dick 180.44 207.65
West Texas 100 6/6/10 RV Blue RV-8 Rovey, Jason 179.91 207.04
Rocket 100, 2010 11/20/10 RV Blue RV-8 Hopkins, Dan 179.74 206.84
Pagosa Springs 100 2009 9/27/09 RV Blue RV-8 McCann, Jim 179.42 206.33
Big Sky Air Race 7/9/11 RV Blue RV-8 Malott, Paul 179.11 206.12
Texoma 100, 2011 4/16/11 RV Blue RV-8 Krebaum, Ken 178.69 205.55
Rocket 100, 2010 11/20/10 RV Red RV-8 Jones, Bryan 177.27 204.00
Pagosa Springs 2010 9/26/10 RV Blue RV-8 Crosley, Eber 177.21 203.79
AirVenture Cup 2009 7/27/09 RV Blue RV-8 Carroll, Alan 176.87 203.54
Memorial 130, Terrell, TX 5/28/11 RV Blue RV-8 Krebaum, Ken 176.41 203.01
Top of the Chesapeake 7/11/10 RV Blue RV-8 Robertson, Gordon 176.38 202.97
BCAF 2011 4/30/11 RV Gold RV-8 Hajek, Jerry 175.16 201.57
Taylor 150, 2011 4/2/11 RV Blue RV-8 Holladay, Chad 174.21 200.48
Pagosa Springs 2010 9/26/10 RV Blue RV-8 Greenberg, Redge 173.42 199.43
Texoma 100 4/25/10 RV Blue RV-8 Stanton, Danny 173.10 199.07
Taylor 100 2007 5/20/07 RV Red RV-8 Jones, Bryan 169.45 195.00
Taylor 150, 2011 4/2/11 RV Gold RV-8 Hajek, Jerry 161.20 185.51
Taylor 150 4/11/10 RV Blue RV-8 Hopkins, Dan 156.48 180.07
Memorial 130, Terrell, TX 5/28/11 RV Gold RV-8A Sutterfield, Stan 190.82 219.59
Texoma 100, 2011 4/16/11 RV Gold RV-8A Sutterfield, Stan 188.88 217.28
Memphis 100 2008 10/19/08 RV Blue RV-8A Labarreare, Chuck 172.70 198.74