I had a stock bottom end 305 Vortec with stock 059 heads up to 280 hp at the wheels. 218/218 flat tappet cam, 1.6 rockers, ported lower intake, volant cold air and long tubes into dual 2.5" to the 2.5" dual in/single 3.5" out muffler. Electric fans and 3 piece march under drive pulley set.
I had basically the same engine with 0.030" over flat tops, a victor jr with homemade plenum divider and a 500cfm edelbrock backed to a powerglide with a 3,500 stall and 3.07 gears in my 1980 Corvette. That car ran a 12.5 @ 112 mph pass on 245 wide street tires. Flex fan screaming the whole pass.
Don't knock the 305 vortecs. They were every bit as potent as the 350 heads. Maybe more so on a 350 with the higher compression ratio. I considered putting a pair I had 1.94/1.60 valve in on my 350 before I put aluminum heads on it and bumped it to an 11:1 383.
The 305 boat engines were 260 hp and 310 tq with the 395' cam. I setup one in a boat with a XM270 cam and headers into a corsa captains call exhaust. Had to make a big prop change. It dyno'd at 290 hp at the prop shaft on a prop dyno with 320 tq. The boat gained about 10 mph from 45 to 55 mph. I tuned the MEFI 4 on it. Added an 02 sensor and closed loop to it. Drastically cut the fuel consumption at 35-40 mph cruising speed as well. 3,500 rpm @ 40 mph after.
