302 motor-light car, about 2800lbs, converter guy said maybe 2 tenth's difference upgrading to an 8''. He told me anything more than a 4500 and it's not going to be real streetable and run hot. Btw what was your Et diff between your 9.5-8'' ? Was yours street driven ?
I do not drive mine on the street. The days of having a streetable race car are over, at least for me. A few too many tow truck calls. And your converter guy isn't wrong. Once you start getting into loose converters, I mean really loose, streetability starts going away; and heat starts becoming an issue. But then again, how much can YOU put up with? Sure I can drive mine on the street, for about 1/2 mile, and then I'm ready to climb back out. When I was younger yes I drove it on the streets with 6100 stall speed. It can be done-if you can put up with it.
2800 lbs is not light, kind of the middle of the road. But you should benefit from an 8". Vane angle is up to the builder. Street driving, you'll want a sprag or mechanical diode for sure. Diodes are more expensive but they are stronger than a sprag. I don't know that you'll see .2, but it may be worth trying. If you don't like it, send it back and have it re-worked; as it's generally less costly than selling it. Used parts are typically 50% of new price.
Converter selection is going to be totally dependent on the data given to the converter builder. Your better off to have every ounce of data, and it's better if you have a dyno sheet if at all possible. And being that it's a street car, prepare yourself for a compromise between streetability and ET improvements at the track. This is exactly why I always say that there is a big difference between a race car and a street car.
And finally, a good converter is going to be $800+. Ain't no such thing as a good quality cheap converter anymore. Case in point, I built the trans for my car and put a Redneck converter in it. After 2 1/2 seasons, I was sold on it-for the money it worked great. One race day the car kept slowing down each round. 6.20, then 6.25, then 6.35, etc. By the time the finals rolled around I was at 6.90 and stall speed was up around 7000 (originally 5300). I was on a roll and wasn't about to quit racing. Took the win on a opponent redlight and idled down the track. Stopped at the trailer and pulled the trans dip stick. Completely full of metal. Had the converter cut open and there was nothing left of it inside, junk. But the worst part was that it also junked the entire transmission. Bushings galled, drums torn up, pump trashed, everything was junk even the case. So that $350 converter took out a $2000 transmission. Started over with the exact same trans but this time I hired a local guy to build the converter, spent about $900 on it and it's still in the car today. That was I think 12 years ago when I put it in. I had him cut it open 2 years ago for freshen up and all was fine. Billet cover, no sprag, good stuff.
The ET difference between the current 9.5" and the 8" I tried was about .05, all in the 60'. It hit harder-but also had a tendency to lift the front end more than I like. In other words on the bumper. The 9.5 is "slower" but more predictable-and for what I do, works a lot better.