truth about 305s.... most poeople hate them because they dont understand them. I jave built a number of them, they make plenty of reliable street power. They use the SAME crank and rods and block as a 350, but the block is casted with much smaller bores. You cannot hog out the bores to make it a 350. However, the stroke is there for plenty of low cost grunt. DO NOT try to stroke it out or get nuts.. keep it to a sweet .040 overbore and its a plenty gas friendly street motor.
trick is do not get crazy with the cam and try to get a set of flat top pistons for it. with that and a performer intake and some long tube 1 1/2 tube headers so it will breathe, youll get 300 horse and torque or a little better at the crank. heres some specs on the last 305 I built for myself, even a you tube link of the car.
79 305 truck block ( ls dipstick)
.040 over, flat top hypereutectic pistons with 4 valve reliefs
callies 350 crank and stage 1 connecting rods with arp rod bolts
clevite 77 bearing throughout, brass freeze plugs
1.5 ratio roller tipped rockers, .454 /.454 gross lift cam
home ported, gasket matched 601 casting heads
cloyes double rolling timing set
melling hv oil pump
summit racing intake and 600 cfm carb
dyno's 321 hp and 342 tq redlines at 5500 rpm (pulls hard all the way to it
realistically it probably gets just under 300 horsepower to the wheels. havent dynoed it yet.
now if you want to wake that motor up on the cheap, invest in headers and exhaust as well as a carb and intake...everything you bolt onto a 305 will go right onto a 350 or 383 later. 305's were designed to get 350 numbers ( in the late 70's and thru the 80's) on a more fuel efficient and smog friendly platform. They were very close and responded nicely to minor upgrades.
Main killer of 305's is that they were built with dished pistons and low compression. Bump up that compression and make it breathe better, it will perform nicely, and still get respectable gas mileage.
thats a link to my last 305 build. I can build you one too. I personally like the 305. Decent street motor that responds well to minor upgrades and still gets nice fuel mileage. GAS AINT GETTING CHEAPER FOLKS!!!