At 1.5 inches you are strangling the intake to the carb pretty severely.

Heres my suggestion.
Source an oval port head from an A14 or A15. To all intents & purposes they are the same. Overhaul it to ensure serviceability.

Source an aftermarket sidedraught manifold for this head type. They are not 'readily available' but they were made & can be found with a little diligence & patience.

Source suitable carb[s], fit carbs to manifold, fit manifold to head, fit head to engine & enjoy all the very best in performance that Datsun has to offer.

The round port head is strangling your A15 & no carb will ever fix that.

Quote:

Yes - that's what I'd like.
There are a few things I have to keep in mind...
As far as I know I haven't won the lottery, I have a big family and a finite bank account.

I can look for all these things, but I'm going to have to pick up a piece at a time when I can find them cheap and do the work (as much as possible) myself.

I'll go check my lottery numbers today, maybe I did win - who knows?