Type 4 Engine build basics, Best approach on rebuild options Options

[TomL]

I am hoping to build a good, solid, higher performance Type 4 which will be used as a daily driver, touring car and perhaps an occasional AX. I have some questions.
1. Are all type 4 engine cases identical? If so, why are "GA" cases preferable?
2. What practical difference is there between a 78.4 stroke crank and an 80mm crank--since the 80mm seems to be more prevalent and a little less expensive?
3. Which is the most preferable bore--94mm, 96mm or 103/4mm?
4. Is there any practical difference between standard 2.0 sized crank journals and chevy sized?
5. Can 1.8 heads be "massaged" enough for decent performance?
6. Pure speculation--What kind of HP might I expect out of an engine with: 80mm stroke, 96mm bore, a moderate cam, re-worked 1.8 heads (8.5 or 9:1CR) and carbs?

Thanks for any answers you can give
TomL