350 Vortec questions / suggestions

[3x2GTO]

I just bought a 350 HO crate engine this week for my 76 C20 and need some advice. The engine is part # 19420879 350/331hp and has a build date of 2021. The first owner ran the engine for less than hour, but I have no idea if he broke in the cam. I did see a 10 second video of it running before I bought it and it's been sitting around for 4 years. I'm the 3rd owner of it, both of the previous owners sold their project cars to LS guys. I'm going to pull the intake to see if it's drilled for a roller cam, if so, I'd like to install a roller cam/kit from GM crate 350/357 engine. My truck is a 76 C20 with 4:10 gears, it's just a shop truck, and a fair weather driver. Is this a good cam choice? Will the Vortec heads cause any header fitment issues? Also, I see where Hooker makes cast iron manifolds. Anyone using these? Thanks!