I have a chance to buy a targetmaster crate engine with a mild cam and I want to put it in my 91 Silverado. It currently has a good running 305 in it with TBI but it can't pull my car hauler very well. What do I need to  consider when swapping the targetmaster motor into the truck? I've thought about the tbi unit and manifold, not sure what to do with the knock sensor, need to add a prom to the ecu, any trans issues etc?  

Ok. This swap is very easy. All the accessories and manifolds will bolt onto the crate motor you want to buy. Total parts interchange, except you'll need to get a flexplate for a '91 350 equipped Silverado, and I'd get a new harmonic balancer too. Plan on replacing all your hoses and stuff while you've got easy access to them, including your motor mounts.

What you need to do is get a new eprom for the truck's computer that's tuned for a 350. My advice, get one from Hypertech. They can burn a performance chip that'll get you the most from the 350.  

Great, thanks for the info.  I thought it would be pretty straight forward but I hadn't thought about the flexplate swap. Yeah, the eprom will help me from leaning out I think as I was worried that the tbi couldn't keep up. The engine has a slight cam which is ok as I need the torque increase for towing.