Good quality tyres run at 30-32 lbs/psi is about as far as you need go.
Rebushing everything and fitting new suspension joints will give you a much nicer ride and driving experience. I'm talking Volvo OEM quality parts not poly. Check and repack wheel bearings, a job that rarely gets done. A proper lazer alignment is a good idea with about 1-2mm toe in. New standard shocks.
State of tune of the engine is dependant on its internal condition and bolting rebuilt carbs and a 123 dizzy to it won't improve it if it needs a rebuild.
The nearer you can get it back to original factory spec the better but a new paint job won't make it drive any better or improve your gas mileage.