Yeh i believe the mk1 turbo delta was the same, standard performance was 130 bhp and where can you find one
It would be alot easier to get 130bhp out of the beta lump
That's true of course but being a turbo it's relativeley simple to extract more if you want to - mine ran 160bhp without I'll effects - getting that from the standard engine starts getting expensive. Getting hold of one could be a long process though !
The later reversed head engines would be more of a challenge to fit but not ridiculously so, the Beta engine bay is relatively roomy after all. I think the N/A 16V would suit the car well but the 8V is a shorter engine (the 16V required the hump in the delta bonnet) so it's more likely to fit. It would shift the weight distribtuion forwards but that could be compensated for - a lightweight bonnet and battery in the boot would most likely do the trick.
Either option would make for an interesting car.