Our Hybrid Intake Gasket Kit includes the correct metal lower intake gaskets to match your original 94-99 3100 cylinder heads and the large port upper intake gaskets necessary to do the large port manifold swap onto a small port 3100 engine. (Please ignore the pic, which shows the small port upper intake gaskets). Heads must be ported to match the roof of the intake manifolds, or you will lose flow and power compared to the stock small port manifolds.
Torquing the lower intake in the proper sequench, to the proper torque, and with a thread locker on the bolts, you won't have to worry about these gaskets leaking again. We supply the information in our articles section, and a printout is included. Plesae check your intake manifold and cylinder head for corrosion around the coolant passages, which will cause a failure regardless of the gasket or procedure.