NOOOOOOOOOOOOOOOOOOOO, in the name of all that is sane, don't spend any more money on that small-bore 305. Find a 5700 Vortec 350 from a '96 to '98 Chevy truck. I just saw two of them on craigslist here in Phoenix, one for $150, the other for $200, both long blocks. I've been helping a fellow CHR rodder on PM and sent him over to buy one of them instead of farting around with the remains of an old flat tappet circle track motor he aquired somewhere.

Look for a sawtooth design on the front of the heads. This will tell you that further investigation is warranted. These heads (L31 Vortec) came in two different casting numbers. 12558062 is one of them (take off the valve cover and look), the other is 10239906. The only difference is that the 906 has (in some cases) separate hard exhaust seats pressed in for extreme duty service and may require a little work with a rotary grinder and burr to fair-in the sharp edges.

What you will get for $200 is a roller tappet camshaft block that is one-piece rear seal and the best production heads that Chevrolet ever produced. It is WAAAAAAAAY easy to get 400 hp and 450 ft/lbs of torque out of these motors and still operate as a mild mannered reporter on cheapo pump gas.