Id say the suck through setup is simpler to play with but also a little more temperamental in the hot climate and as far as I remember there still is a fiat ritmo fwd hatch with a fiat tc 2 ltr in Perth that runs the same setup with a weber and water spray and he often blows away the big guns in his little 700kg missile in the SS series it makes about 300 rwhp. He has no probs without intercooler / injection.
L18 do the maths on the compression and boost figures. Look at turbo sites and maybe some real life figures and details for guidance. Ive got one of those ignition control units from Jaycar it was plugged into an alfa 2ltr dont know anything else about it or how you can modded to run in other engines?? Your theory on retard sounds good if it can be done. Do you know any other details on the engine???? dizzy etc???