It's a bit tricky with the down facing exhaust ports isn't it?
I am also in the process of making my manifolds, I will be using 40 schedule stainless steel weld els and will try and make them 4 tubes. It is taking forever. After I thought I had it, I installed a spare engine in my '79 and had problems with them hitting the steering shaft. Had to change everything.
Luckily I didn't have them welded yet.
If I can't get the 4 tubes to work I will probably use the same method you are using.
I will be going blow-thru and intercooler route though, till I have the cash for an EFI setup.