Is this worth it? 1974 440

What motor was in the Valiant? If it was a small block, keep the motorhome water pump housing since it dumps out on the same side as a SB radiator. If there's nothing wrong with the water pump don't change it either as it is a special high flow pump that's not available any more. Motorhome motors often used moly rings so if you do decide to do an overhaul you can probably order std. bore pistons and get away with just rehoning (if it even needs it). The 452 heads have induction hardened seats for regular unleaded and flow just as well as 906's for what you are doing. Steel shim head gaskets will help a little with CR if you once again decide to overhaul. About the biggest performance upgrade for the buck you can do on the cheap is put in a new cam and lifters as the stock cam lift will be around .363" lift. With stock pistons I'd stick with Lunati Voodo 60300 or similar size cam from other venders that way you won't need to change springs or anything.