HI IVE GOT AN 83 S15 PROJECT WITH A 305 HOW CAN I GET THE MOST POWER OUT OF IT AND WHAT SIZE REAR END GEARS I NEED FOR BEST PERFORMANCE ITS GOT A STOCK REAR END WILL I DISTROY THAT REAR END IF I LEAVE IT THANKS FOR YOUR TIME  

just a heads up, you're gonna get blasted with posts to ditch the 305 and get a 350. some places to start to find performance for your truck...there are about 3 different threads on the carcraft site that ive been a part of, theres my thread on making an s10 stop, that discusses how well the stock brakes will work. popularhotrodding.com has a couple of good articles on building a 305. as far as rear gears, you need to know what cam and convertor you have or are planning to put in. also, are you dragging or doing some spiriting driving. pm me with some more of the specifics of the truck and what you want to do with it and ill give you my take on everything.  

Yup...your money is far and away better spent on a larger bore engine.  If you insist on using the 305...a small cam, decent intake and carb, small headers are your best bet.

I wish I hadn't dumped ANY money into my IROC's 305 when I had it...much less the amount I did...

Oh...and that 305 isn't going to hurt the rear end (assuming you stay on roads and race tracks)...even if you do build it up.  As weak as the 7.5" 10-bolt is...the 305 won't make the power to hurt it (assuming you don't manage to figure out a way to run 20 pounds of boost or a 400 shot of nitrous).  

I think the 305 is capable of making good low end power, but you wont get it to rev up. so put a dual plane intake, and like a 500cfm carb on it and stuff in a mild cam. With that small bore you're limited on the heads you can use but they made hi-po 305 heads for f-bodies and monte carlo ss's. on the otherhand you would make a lot more power for the same work with a 327 or 350 to start with.  

Here is a combo that I use in a costumers engine I use a set of s/r torquer 305 heads with a .477 lift lunati street master cam & lifters P#07101LK and a speed pro double roller timing set P#cts-3100R and it runs strong.What transmission are you using in the vehicle.