Chiphead,
I'd use a 600cfm instead, performer RPM or just the plain performer. See the 750 a li'l bit bigger than needed. If the engine is apart, why not changing the crank for a 350 one and new pistons for a 350 engine, that one seems logical to me when You say You do not like the 327. Have in mind that everything else is just the same, basic diff between a 327 and a 350 are the crank and pistons.Of course refering a 327 68 and up.
Just check to see, but the vast majorities of the 350 cast cranks have a cast number finishing in 2442. A forging would be better, but more $$.
As for the jets, for a 600 cfm holley, if using cast iron exaust manifolds in a 327/350 I'd start with 65/72, and check to see how it turns out. If it has headders, try 64/71 or 64/70. Guess it's pretty close to the perfect set up.
The 20w50 is a cool oil if You are in a hotter place. Ocassionally I use always this weight on my cars here.
Just my 0.02.
