1991 S10 pick-up truck engine size ?

I have a Haynes Repair manual with pictures of several S10 motors. It shows both a 2.8L V6 (TBI) motor and a 4.3L V6 (CPI) motor. The placement of engine components looks like the 2.8L, so I assumed my motor was a 2.8L . But a friend looked at my truck , and he said because my Vin# had a Z , that my motor was a 4.3L . Do they make a 4.3L motor with a TBI injection system ? The manual showed only a 2.8L with the TBI injection.

I need to be certain of the motor size for buying parts and oil changes. The manual says the 2.8L holds 4.5 QT. of oil and 5 QT. for the 4.3L . But since I thought it was a 2.8L , I have been putting in 4.5 QT. at oil changes. Which , according to the dip stick , filled up the oil pan.

Feedback on this issue will be appreciated.1991 S10 pick-up truck engine size ?
Call a dealer with the VIN1991 S10 pick-up truck engine size ?
There SHOULD be a sticker somewhere under the hood of the truck giving engine size and type, hose routing and other info.....

The 4.3 looks exactly like a 350 V8, only a little shorter, since it's based on the 90 degree 350. (same bore and stroke, only with 2 less cylinders.)

The 2.8 is a 60 degree V and is a good bit smaller in size that the 4.3.

If you have a bud that's pretty familiar with these engines, he can spot a 4.3 in about 2 seconds.