Couple of things I learned the hard way:
Buy a new carb. Don't bother with rebuilding an old one. You'll end up at the same price point in the end.
HEI: I went with an ebay EFI distributor. It lasted 2 years before going bad but it was cheap so I just bought the same one again. Also be sure to remove the resistance wire from the firewall to the distributor.
Do it in stages. I started with Langdon headers and made my own heat plate. Just get the Langdon heat plate. You won't save money making it yourself. Sealing it is a PITA. I used a ton of RTV.
As far as staging goes here's the order I'd do it in if I did it again:
1) HEI and electric fan. Runs so much smoother that way and frees up a couple ponies. I used a pusher style fan and bought a 3 core radiator on Ebay. came out nice.
2) Offy intake and carb. Use the exhaust heat for now.
3) Langdon split header and exhaust. Heat the carb with water. A couple ways to do it. I tapped into the heater hoses at the fire wall. Others tap into the front of the engine. If you have a tapped hole on your thermostat neck that'll make life easier.
4) Cam. On my Camaro I was able to change the cam by pulling off my grill, unbolting the engine mounts, and jacking up the engine. This gave me just enough room to pull it out the front. You'll also need an aluminum cam gear when you do it and new valve springs. Lifters as well.
5) Head. This is where that spare engine might come into play. Get lump ports and oversized valves.
6) Transmission. I had a powerglide. Swapped to a 2004r. HUGE difference. I highly recommend this one. You can get them used pretty cheaply, wire in the lockout, new linkage, and gear selector bezel. Worth every penny!
7) Gearing. Once you have all that done you can now get better gears.
I guess those of us with 1975 to 1978 cars with integrated heads have to combine steps 2, 3, and 5 into one step. Although that's a good time to do 4 as well. Not sure on which year the Varajet integrated head came into use on trucks.
