Keep everyone up to date with how your project is coming along.
I have a 1970 mach1 mustang and I want to build a motor. I have a 351 Cleveland standard bore block wanting to get around 500hp streetable power do I go 393 stroker or stay with the standard 351 bottom end. The next is do I stay with cast heads or aluminium trick flow or ch1 and what cam
i would strongly recommend you check out the various forums that specialise in these engines, as they will best be able to help you.
500hp is certainly do-able from a 351 - although I would suggest a 30 thou rebore to ensure a perfect bore and the option of a better piston design and material. A stroker kit will certainly make it easier to realise, with a bit more torque as well - but is it worthwhile?
There are many things to consider, the first usually being budget - be honest with yourself as it WILL be more than expected.
Problem is, there are many ways of doing so and you haven't given very much to work with - things to consider are...
What fuel - 89, 93 E85 or what? That will affect the compression.
What is the base engine - 2V, 4V heads? Which versions of them and their condition?
How will the engine be used - are street manners important? Is it primarily for the track? is economy important?
Do you want a hydraulic or mechanical, flat tappet or roller camshaft?
Is bonnet/hood clearance an issue? That will affect the choice of intake.
Stock exhaust manifolds or headers?
Carb' and distributor or full EFI package?