I have a pair of stock 454 mags in my 35 lightning with silent choice. Are my risers on my stock cast iron manifolds "standard height" or would there be a 3 or 6 inch rise in them?

Not sure about your set up but my 85 10 meter had 3" riser blocks and then a 7 degree 4" elbow before I changed it to stainless marine manifolds. Hope this helps.

Should be standard height unless it's a triple or staggered.