As point of references...
Original Customs 2056 Type IV
Original Customs 1911 Longblock
Porsche 914
1.8 heads can work, with some porting and polishing.. They just won't be as nice as 2.0 heads.
While prices may vary, you can likely pick up a lot of info from these type IV builders.
For many years, the "easiest" and reliable upgrade was to put a 2056cc in a 914. Depending on cam, and carbs vs FI, 110-130hp was possible. And it was also plug and play. These motors are only getting older and perhaps even more $$ to upgrade. Finding quality components is one challenge. Finding someone who knows the motors and what to expect is another.
150hp type IV motor would be a lot of fun in a 914 for sure.