Stock flywheel is 21 lb. A very popular alternative is the 17 lb. steel billet flywheel from SHO Source. They also sell a variety of 8 lb. and 9 lb. aluminum flywheels with a steel insert.
The aluminum flywheel will make your car rev like a superbike. Pain in the ass when it comes to resurfacing, though. They can be resurfaced at the most once before the steel insert needs to be replaced. SHO Source has inserts.
Multiple Allen bolts may have to be drilled out. Your Allen key may finish up looking like a meat skewer.
Bolts required are Flat, Socket Flat Head Cap Screw, #10-32, Steel, Alloy Steel, Black Oxide, 1/2 in Length:
SHO Shop, earlier design, through at least 1997: 6 1/16” i.d.
SHO Shop, later design, from at least 2002: 6 1/4” i.d.
SHO Source flywheels and inserts use the later design. However, the insert won’t work on the old style flywheel as the inner bolt holes in both cases are drilled 3/8" from the inside edge. Consequently the inner holes will be 3/16" off. No known source for old style inserts.
Nick Chrimes, BaySHO Performance