I think this is what I have:

New Venture 1500

5 speed fully synchronized transmission, with bell housing integral to aluminum transmission case. Similar in design and appearance to HM290, 5LM60, and NV 3500 series transmissions, but slightly smaller. Requires some special tools to rebuild. Used in 1996 and up GM S10 vehicles with 4 cylinder or 2.8 liter engines.