I did a similar swap in my 1985 Cutlass, but it was a 231 V6 car. I found a complete 1985 Grand Prix with factory 305 power and pulled all of the brackets and the crank and water pump pulleys off of it. The 307 alternator will probably work, but you will need to re clock it and put a nut on the end of the adjusting bolt as the 307 alternator is likely not threaded. I used a 307 alternator from a wrecked taxi when I did my swap, so it can be done.. You may also need a Chevy 305 style fan shroud and fan/clutch assembly. For the A/C, I am currently finishing a hybrid setup for mine consisting of the hoses from a 1984 Camaro Z-28 with the HO 305 as well as the compressor brackets from that car so that I can use it's factory dual snorkel air filter housing and hoses. I may have the hoses rebuilt a foot longer so that I can use the F car hose brackets that mount them to the core support.( G car and H code f car hoses are different than the F body G code hoses) Oh, don't forget the starter and switching the battery to the passenger's side. Finally, don't let the battery positive cable to the starter rest on anything that can chafe it as it will wear through and start a fire....don't ask me how I know... As for cooling, I run a $35 radiator that I pulled almost new from an 83 Cutlass with a 307 and it cools just fine with the factory clutch fan, $15 parts store water pump and a 160 degree high flow thermostat. My engine makes around 350 hp ( according to Dyno 2000), so it's cooling needs should be similar. You will also need new radiator hoses, and a new pressure hose for the power steering, in addition to a Chevy Power Steering pump as they have different pulleys and brackets. You should be able to find one for under $20 in a junkyard ( I pulled my pump from a
Caprice, and the hose from the Grand Prix that donated all of the other parts). Another thing I found is that not all motor mounts are created equal. Some of them require that you have an old mount to begin with and only supply the rubber insert, not the whole clamshell. You need the whole thing, so shop around and inspect the mounts before you buy them. I'd also look at the rear axle and consider finding one with a better gear ratio than stock. I pulled my 3.23 axle for $75 from a 4 door v6 83 Regal that had it as an option ( I decoded the data sticker on the trunklid to find it). It makes a big difference compared to the 2.41 axle mine came with.