If you have to put on a line, don't make it any bigger than #6. IMHO, it's a waste of effort. Make sure that the clearances are correct and that the lifter bores do not have excessive clearance. That's where a Cleveland will bleed. Measure the pressure at the back of the block. If you run an HV pump, get a big baffled pan to make sure that the pump stays in oil. Deburr an HV pump, run a moly shaft with it and watch your distributor gear. At under 5000, I'd stick with a stock pump.

I don't use a line, have over 700 runs right now and the oil pressure hasn't changed at all. Actually, I have zero mods to the oiling system. Small block Mopar's have a way worse oiling system than any Ford and you almost never hear about people hacking the crap out of them.
[addsig]