Welder - look up vocational schools around you that have a welding program. They'll probably charge you a shop fee of say $5 or so, & you give the 'student' $10/$20 for their 15 mins to TIG weld the throttle linkage after you've removed the stock one on the marine intake. You can swap the stock one from your blazer over & forget the welding etc, you'll lose a bit of air flow though, not crucial.

Cam - call Lunati, Comp Cams etc & talk to them about what you have, what's going in & what you want. They'll suggest cams & cam packages with springs, rockers etc.
I have Comp Cams Ultra Pro Magnum rockers & they are sofaking sweet!!! Rebuildable, strong as hell & with the Lunati stage 2 torque cam with double springs (bad idea, old technology, get bee hive springs if you decide to swap them out!)
330in/lb springs aren't really needed in a DD for the cam I got because it won't be seeing sustained high RPM's for long periods of time. They have the high pressure springs to avoid valve float & sustained high RPM's. IMO

Porting - It's always a good idea to port & polish the heads, especially if you have forced induction... but it's not necessary.

A/C - The Wynjammer doesn't effect the A/C at all. It mounts on the engine with the plate they supply & the A/C works normally.

Rex - <--- Amen!