I am building a Buick Skylark 350 for street/parking lot use. I do not want to use long tube headers and can't find anyone who makes shortys. The original manifolds on my 1968 engine accept 2" down pipes. Do any of the later manifolds or those for a GS accept larger or am I going to be stuck with modifying a set of Chevy 350 shortys for a Chevelle? Unfortunately the exhaust manifold casting number reference doesn't list the down pipe sizes.