That is pretty much the exact route I went with my first mustang. When the 200 was tired I swapped in a 250, tossed on an Australian head and a weber 38 DGES carb, and a clifford 3-1 header set. The difference was absolutely astonishing. You would be surprised how strong one of those little 6's can be when you get them to breathe.The 1 barrel to 2 barrel plate works but you loose a lot. It would be best to put a 2 barrel intake on it. Another great upgrade is the split header. These engines also need a better distributor. If you want to continue, you can get an Australian head and run a better cam. The difference would be astounding compared to the original engine. The better engine to start with would be the 250 though unless that is what you already have.
Ak Miller - theres a blast from the past! Turbocharged Pintos brochure I have from c. 1973:OVER 50 years ago went the Alk mILLER ROUTE AND installed 4 Honda 750 carbs. Car long gone traded in on my new 69 GT350. Kinda chuckled when he stated my 67 Sprint was a girly car. It would wip most SBFs back then being in the low 13s