Will a 350 Chevy motor bolt up to a 91 s10 that has 2.8 manual bellhosing?

Yes, a 350 Chevy motor can be bolted into a 1991 S-10 with a 2.8-liter manual transmission, but you will need an adapter plate to connect it to the existing bellhousing. Additionally, consider upgrading the transmission to handle the increased power and torque of the 350 engine, as the 2.8's components may not be sufficient. Proper modifications to the engine mounts, exhaust, and possibly the driveshaft will also be necessary for a successful installation.