Have some ?s off I use 85 caprice driver manifold connected to a 85 c10 passenger manifold with a crossover then cut the passenger manifold nd add a flange will it effect flow

 

Depends on how much power your already making, as well as how much you are looking to make. Why not just get a used tubular header setup for a SBC for cheap, flip the passenger side header and weld it any way that you want to. Much easier to do...

 

It's a budget build so using what i got

 

Those manifolds will work fine.

 

Then yes, it will have a negative effect on flow. Think of what your doing. Building a twin turbo setup using two exhaust manifolds is restricting enough for each turbo because they do not flow very well, but now your plumbing eight primaries into one exhaust manifold that has less than 2 1/2" in diameter for the turbo sitting on top of it. It will work for a budget build, however yes to your original question, it will be detrimental to flow...

 

I agree with Street. That setup will only be good to about 600-700 HP. If you need more flow go with a tuned header. The manifold has the advantage of more energy to the turbo due to less heat loss from thicker material and less sq. area.
Usually budget build turbo setups are on budget build sub-600hp engines so the manifolds are a good fit. Throw some stock manifolds on a junk 250-300hp engine with a tiny cam and 15psi and now you have a 600hp engine.

 

I'm aiming for at least 500 max no more for a daily driver thanks for feedback on my question