[scooder]

Arp hardware is overkill on most all flatheads. Have you checked the price of an arp head set of studs!!!!!
If your intention is to bolt it together and not open it up for as long as possible, use head bolts, don't need nothin fancy, Ol' Ron uses grade 5 with complete success.
Keeping stock heads, cut them for 0.050-0.045" piston clearance. Helps throttle response, ads a bit of compression, adds torque, better on gas.
Stock cam, best for low down torque.
Valve setup, you may already have hardened seats on the exhaust, they phased them out on the 8BA style block.
Nothing wrong with stock guides and valves, they worked from the factory forever, nurled guides is a good way to go.
I'd also go with stock type lifters (non adjustable) they can't go out of adjustment, and you said you want it to run well for a long time.
I realize my suggestions here arnt expensive enough for some.
Martin.

Forgot something, you mentioned a brace for the center main, again no real need for your engine, but if it makes you feel better fit a simple strap.
oil pump, can yours be rebuilt? No need for high pressure or volume stuff, late stock pumps are great.