308 or RHS on a 408

Any 360 heads on a stroke 360 motor will run ok.

And yes the D66 is a great intake but beware the D66 intake has small ports like the 273-318 heads. Really no problem power wise I believe since the ports are short. I am using two 500 cfm Carters on my 340.

Get this Fel-Pro intake gasket ! It has a steel core and will not rip / split if tighten hard. You can just barely see the print-o-seal rings but twice now I have had no intake leaks using this gasket.

Fel Pro 1213S.....the S is for steel core, you do not want the 1213 gasket without the S cause the small ports may crack the gaskets. Some places you get like only a 1/8 inch to seal--but it seals good with just some high tack / Indian head sealer just on the head side. The gasket is so nice you can remove the intake, even after a few years and reuse the gasket. It sticks to the heads only. Use rtv on the end rails only.

I drill a small hole on each gasket for the exhaust heat.

http://www.summitracing.com/parts/FPP-1213S-3/