sundown
+1y
going from a normally carbed powertrain to a efi powertrain has a learning curve to be sure. but to get factory mechanical guages to work with a efi system is typically not that big of a deal. There are electric to mechanical guage converters and in some cases you will be able to make a mechanical guage work in place of what normally would have been an electrical connection by just plumbing in the mechanical gauge's sending unit. Either way, a speedo shop would come in handy as they would be the most familiar with specific parts you might need when you pick out your engine combo.
On the sho engine, your right, its only downside is it being on the large side but its not overly huge.
Like david mentioned above the 2.3l pinto engine would be trick but thats pretty common and expensive, same as the supercoupe and the turbo coupe conversions.
Speaking of the 2.3 ciricle track engine, back in the 60's another inline 4cyl was common on the circuit and seems to be quite rare to see in vehicles these days and thats the old Pontiac slant 4. Its the old venerible pontiac 389 split in half. pontiac modified the block mold to only pour one half, one side of the engine. lots of go fast goodies, standard pontiac v8 rods and pistons, same bearings in the bottom end. Its fairly small being a 4 holer and it uses the BOP trans bolt patern, so you could do any number of manual trans swaps or auto overdrive swaps (2004R comes to mind!!) The down side is the whole cross branding issue that you talked about earlier, but you are possibly considering that anyway with the vw and toyota engines...
The 22re is the electronic version of the 22r. efi and all that jazz that goes along with it. Most deff a bulit proof engine. Would be a good choice to be sure.
Man its fun to sit and think of the possibilities...