Sonny,
We just went thru the oil cooler ordeal on a newly finished RV-8 this summer.
Started out with the Niagra 20002A supplied with the firewall forward kit for the IO-360. Mounted it on the cyl #4 rear baffle. The high compression ECI IO-360 engine simply overwhelmed this small cooler.
Next we tried the Aero Classic 20006A-equivalent 13-row cooler. Fitting it was a bit of a problem, it was just simply way too physically large and rubbed the motor mount and cowling a little bit. It also cooled way too much. Overkill.
We finally bit the expensive bullet and got the $600+ Stewart Warner 10599R cooler and the fit is perfect and the cooling capacity is perfect. Oil temps now in the 180-190 range and maybe reaches 210 in hard prolonged climbs on a 100 degree Texas summer day.
There is a less expensive option... the Niagra 20004A or Aero Classic 8000081 cooler. It's got 10 rows. Plenty of thermal cooling capacity for most IO-360 engines and it's a bit smaller (roughly same physical dimensions as the SW 10599R). Spruce sells the Aero Classic for $255.
The RV-7 looks to have a little less width than the RV-8 for mounting a cooler on the Cyl #4 rear baffle however, so you'd better measure very carefully to be sure a 9 or 10 row cooler would fit there. If the 13-row cooler hit stuff on the RV-8, there's no way it would fit on the rear baffle of an RV-7. It could fit on the baffle/inlet lower ramp up front if you don't have your air intake filter mounted there. That's where our air filter is, so we could not mount an oil cooler up front.
In retrospect, we wished we would've bought the expensive SW cooler first... it would've saved a lot of hassle and extra expense. It's a positively known-to-work well cooler. Sometimes airplane parts are just crazy expensive and you just gotta pay what they cost.