I haven't tweaked my wife's 740 NA (she loves it stock), but have
modded my 244 Turbo.

Things I've done that I'd suggest:

Front and rear IPD swaybars.

Lower with IPD springs.

Shock / strut upgrade.

Support / stiffening rods, as available.

Turbo upgrade: I got one from an aftermarket company in Colorado, it is
bigger and pushes a lot of air; there is greater low-end power and more
turbo lag, but my god it is great when spooled up: effortless.

I put on the most aggressive rubber the wheels would take.

Had the head tweaked and enhanced for better breathing and
near-indestructibility.

Replaced the engine compartment wiring.

I still plan to change out my exhaust (goodbye, cat!) to a wider pipe:
that will make a definite difference.

I haven't tweaked my wife's 740 NA (she loves it stock), but have
modded my 244 Turbo.

Things I've done that I'd suggest:

Front and rear IPD swaybars.

Lower with IPD springs.

Shock / strut upgrade.

Support / stiffening rods, as available.

Turbo upgrade: I got one from an aftermarket company in Colorado, it is
bigger and pushes a lot of air; there is less low-end power and more
turbo lag now because the vanes are bigger and heavier and take longer
to spool up, but my god it is great when spooled up: effortless power
at speed with seemingly endless reserves.

I put on the most aggressive rubber the wheels would take.

Had the head tweaked and enhanced for better breathing and
near-indestructibility.

Replaced the engine compartment wiring.

I still plan to change out my exhaust (goodbye, cat!) to a wider pipe:
that will make a definite difference.

Wow, that is one super rusty engine block, the manifold sure looks nice
though.

What's the purpose of cutting out the drain bung in the block? I didn't
look at every pic yet.