I found a pair of 906 vortec heads for $300 i wanna use on my 350 build im usings a 70s era block so with the vortec heads do i use a roller cam with lifter or flat top cam with hydrolic lifters?

You would have to convert to a roller cam which those kits are expensive.

Heads don't care what cam / lifters you use but your block is a flat tappet block

so i could use them vortec heads with a flat toped cam and hydrolic lifters right?

Yes you could.The roller hydro conversion kits cost kind of work out to you could find a good roller block for less than it costs for the kit.Most good shops have moved to put pressure on their customers to use a roller cam engines because the lack of additives in today's oils which create flat tappet cam failures.You can use a additive during break-in of the cam,but I suggest you continue the use of a additive in every oil change through out the life of the engine.