Hy guys have a 502 1996 up mark 6 engine it comes with roller cam from factory with guides and spider hold down plate.If its possible to use an 1970scam,lifters,chain and pushrods? flat tapped cam.If It will be where i can get aftermarket timing cover?

Angel,

you can use a flat tappet cam in your Gen VI block. You should use the camshaft retainer plate that comes with a GM Gen VI timing set though. The lifter bores are .300" taller which should not pose a problem using flat tappet lifters. I don't definetly know of an aftermarket T'chain cover off the top of my head but I believe Cloyes has one or is about to offer one.

Keep in mind your cylinder heads valve train parts will need to be converted over to be adjustable by adding screw in rocker studs and using long slot stamped steel or roller rocker arms.

You can get a flat tappet grind using a Gen VI core from most, if not all, cam manufacturers. This will allow the use of the Gen VI T'chain and cover..an option to think about.