I had some flanges made up for the exhaust and intake ports for the Frontenac head to make manifolds with. Both flanges are the same except for the inner diameter. These are laser cut 3/8" mild steel plates. The exhaust are sized at 1.5" holes (Quantity 3) The intakes I made a touch smaller at 1.25" hole (Quantity 2). The bolt holes are right at 5/16" diameter, and they will need to be opened up a little (holes in head are 3/8"). I had them made smaller as I detected some slight variance of bolt spacing so you can just drill them bigger to open them up until they fit or offset grind as needed to fit the specific bolt spacing of the port. They will not bolt on as is. These will fit Frontenac T, S and I believe R heads. If you have any questions of fitment, please ask first. I only have 2 sets of these to sell, I only had these made as a one time deal, I do not plan to offer these again. Price is $65 shipped within the US. I accept and prefer Paypal friends and family (so no fees), or your check or money orders. Contact me by PM or via email, crazydart400 AT yahoo DOT com. .