90+4MM @ SOME DIFFERENT RING TYPES AND HOW THEY GO ON @ *HEAD_GASKET CT90K0_to_K4 (ATC90_F/N_TO_1113934) ALL_S/SL/CL90'S ALL_CM91 12251-028-030 1/20M (R2192)THIS IS THE ALL ROUND HEAD GASKET THAT THE CT90K0 THRU K4 TOOK AND THE EARLY ATC90'S THE NEWER CT'S AND ATC'S HAVE THREE NOTCHES IN THE HEAD GASKETS. THE ALL ROUND HEAD GASKET WORKS FOR (CT90K0 THRU K4) OR AN ATC90 WITH A ENGINE SERIAL NUMBER SMALLER THAN 1113934 R2192 @ CT90 ATC90 ATC110 ST90 NEWER STYLE HEAD GASKET 12251-028-790 7/21M (83w)THIS HEAD GASKET WORKS FOR (CT90K5 THRU 1979) OR AN ATC90 WITH A ENGINE SERIAL NUMBER LARGER THAN 1113934 83W