Not 100 percent sure on a street heat, but my Edelbrock, and several others, the size from intake to head port is a fel-pro 1250. Can get them at your local auto parts store, may be a next day order item, but they should not charge you shipping etc. Whatever you do, make sure the gasket is not smaller than the port transition. I would get the 1250, start from there, and if not spot on, exchange it for next size up or down. Your stock head ports will be smaller than the intake ports on that intake so transition will not be ideal, but no sense in adding to that with a gasket that is too small. Hopefully someone with that intake will chime in on the size/part#. Hope this helps, Joe