Valve springs or Suspension springs?

I've never had any luck using anything but stock springs for dirt work. Need more height? Just pack them up with spacers. I like to use the '74 style spring too.

Valve springs? If you can't add material to the exhaust ports & since we don't have F or smog B heads here you only need 4 duals just for the intakes. For a cam, a Wade 140 on the intake (240@.050" with .297" lobe lift) & a Wade 185 on the exhaust (it's a Cosworth for Kent engines 252@.050" with .274" lobe lift) would give you a good cam that lasts forever.

'73 cars are crap compared to the earlier ones, all the sheetmetal is thinner & the A pillers crack very easily when you give them a thrash with a big front sway bar. The side window glass is thinner too, worth swapping too to save a few kilos.