Well.. Yes and no. It is possible to bore a 1600 to 80 mm, if you can stand paper thin skirts at the bottom of the liners, been there done that. If you have money to finance a machinist's kids college education, you can open up the liners bores in the block to take shortened or custom 1750 shorty liners that can be opened up a little more.
With cranks, about anything is possible. I have been exploring big bore 1300's that require short stroke crankshafts, 67.5 or 68.5 mm. I found that custom stroker or de stroker are ONLY a couple of grand for real good ones.
Limiting factor here is rod big ends hitting the inside of the block. Splitting them at an angle helps a little. Carello can make you custom ones, $1000 + each, but you only need four
.
Finally, Alfa offered the following 1600's; regular flavored 78 x 82, or (
) 86 x 68.5, using the 1900 mono-liner set up, though I believe this used a special 1750, not 1600 block.
If you are a machinist, or have money, about anything is possible
I suppose! ( I didn't tell you about the head work, or pistons, did I?)
Gordon Raymond