1988 V20 steplift/305 chevy, mercruiser drive.

[spareparts]

88 should be an Alpha 1 generation one. The top cap on the upper unit should have a flat top. Gear ratio should be stamped on the side on one of the decals. You're gear ratio snould be 1.65. IF you happen to pull the upper unit apart, drain the lube and look for small marks on the teeth, they should be timing marks(only on the 1.65), the gears will have the same number of teeth on each gear. Lower unit should have plastic insert type water pick ups vs molded in water holes. The only way to be sure you're lower is an Alpha is when you drop the lower to do a water pump, it shouldn't have a small spring loaded pin on the vertical drive shaft. If you decide to build a 5.7, you can switch to the HD 1.5 gear ratio upper gears, just know it takes specific tools to set up the gears