Michael, a couple of points, if I may?
1) the RV8 will need an approved position source. Upgrading the 430 to 430W is an expensive path. Consider, rather, selling the 430 and installing an Avidyne IFD440 in the same tray. A bit more money to get a brand new GPS with a better user interface
2) the 330 is a different form factor than the 327. Check available depth behind the 327 tray as the 330 is longer which might make this swap a bit of a challenge from a mechanical standpoing.
While the upgrade of the 330 is a relatively inexpensive thing to do since you already own the 330, the other costs of the 330 are significant to others who may be considering installing a 330. It's heavy, power-hungry and takes up a fair bit of panel space. For some who don't already have a 330 in their panel, consider other options such as the Trig TT22.
For those with a KT76 that might be of dubious longevity, it's worthwhile to look at the Trig slide-in replacement transponder, the TT31. With an appropriate position source you could easily be 2020 compliant and have a solid solution based on Mode S-ES.
As for position sources, even those folks with a straight GNS430 might want to consider a less-expensive solution like GRT's SafeFly GPS module. At $500 it's a lot cheaper than a WAAS upgrade on a 430.