What is a good combo for turning high rpm?

If you need to stick with the 318, I would use a lightweight 3.58 crank, change the pistons and do some oiling mods.
You won't get much power at 8000 with those heads but you can probably get them to pull to 7000rpm with maybe 400-500 rpm overrun before power falls off fast.

If you can change heads, simple W2's will allow what you want, with TD rockers you'll have stable rpm.
What do you use for fuel?
I'm sure you can get some usefull high rpm power and reliability with the sb mopar. If you need to save weight, Indy's got a 210cnc port in their sb heads that works really well. You can use a victor intake if hood clearance is an issue. Keep compression as high as you can with whatever fuel your running and pick a cam with an rpm range of about 600rpm lower than the max rpm you want to turn.
You could use the 318 crank but I think the extra TQ through the rpm range will make the car better even if you don't hit the 8000 mark.
Brian