I've been thinking about changing out my stock 5.0 V8 in my 85' c10 for something with some HP up near the 300's. Would I need to replace the tranny at that power level? I'm not sure about how many horses it has stock. I'll guess somewhere in the low 200's. Because the engine was sitting around for a few years until I got a hold of it any suggestions about simply rebuilding the engine instead of replacement would be greatly appreciated.
what kind or tranny you got? im pretty sure your tranny could handle 300hp.
Keep the engine you have and order a crane cams 268h series cam and lifters for it. 230 bucks or so. A set of headers with at least 1 and a half inch outlet and 3 inch collectors. A good 750 cfm edelbrock and you got your 300. The tranny shouldn't have any problems as long as it is well maintained, however I'd suggest a shift kit.Your 305 should make around 180 horses as is stock.
I'd say your engine stock is somewhere between 150-160. There are a lot of things you can do to a 305 to wake it up. A 305 is basically just a short-stroke 350, so most of the parts that will work on a 350 should work on a 305. Depending on how much you want to do, you might be better with a 350 crate motor, but there should be plenty you can do with a 305. As long as you don't get too crazy with the HP and mods, your stock trans should be fine. Probably the first thing I'd do is install a trans cooler, though. Just to be on the safe side.