Talk to Gary Pavlovich - he is the guru on these engines and can provide all the advice/parts you need, including custom camshafts. Mine is currently being re-built - I have the Weiand 7503 manifold but it's not that good apparently, especially for low down torque. I was going down the stroker route at one stage but the extra complexities of custom pistons put me off - if I was in the US I would have though. Search for Gary on google and you should get an email address - if not I can pm you, he's very helpful and wouldn't mind I'm sure.
PM sentDo you have Garys email I can't find it on line
Thanks