If it were me, I would save my money, and run stock (OEM) intake and exhaust. The 258 is a low rpm workhorse. You very well could slightly decrease your HP running a cheap header that will rust out after a couple years anyways.
If it were me, I would save for TBI or EFI. A junkyard TBI can be built for a hundred bucks or maybe a little more depending on the adapter.
As for the engine, prime the pump, and run a compression check and go from there. Read the plugs while you are at it...
79 CJ7 "CJ Express" 4.2L, NV4500, D44 rear
69 800 with SBC, SM465, NP205, 14BT