recommended oil weight

[jfd3604]

I have recently purchased a 71 C-10 with a 396 with the following options.
396 ci engine, Pro-Form 750 4 bbl, Street Dominator Hi-Rise aluminum intake, roller rockers, Bowtie aluminum heads, Hooker Super Comp big tube headers, HEI distributor. The engine is approaching 500 miles and I think i need to do an oil change since the engine should be broke in by now. I have not been able to locate the original builder to find out more about the cam etc...
My question to all would be
What oil weight should be used in this engine knowing the information above.
Hope to post some pictures later on.