Personally I would be looking at 75s and 85s as it was easy enough to
upgrade.

Not necessarily. If you wish to upgrade a Luscombe 8A (65 hp) to a higher
engine, you must remove the fuselage tank and install wing tanks. Doable
with some cash and time with metal wings however, you must manufacture the
tanks yourself if you have fabric ones.

Don Swords of Don's Dream Machines (770-412-8885) is about as good as you
can get for overhauling A-65s, C-85s, C-90s and O-200s. He's not cheap, but
if you call him he will talk to you all day about any questions you have.

Good luck.

Deb

1946 Luscombe 8A (his)
1948 Luscombe 8E (hers)
1954 Cessna 195B, restoring (ours)