What’s the best new high hp motor that will fit in a 72 Scamp?

True “bolt in”?

Blueprint stroker, or have something built.

Unless someone has some NOS blocks kicking around........ I don’t think you’ll be getting anything that’s actually “new”.

Not sure what’s involved with putting a G3 in it.
I’m guessing it’s not a “bolt in” operation...... but it might be.