I have a 98 GMC pick up with a 4.3 V6 and would like to replace it with a 305.
How much trouble will this be?

Well, it all depends on how you look at it. On the one hand, they had V8's in 'em so no big deal. Everything you need's at the wrecking yard or on a doner truck. But on the other hand, nothing will be interchangable from V6 to V8 (cooling system; trans; electronics; exhaust; etc.) so that means starting at the grill and working your way back to the tail lights. If you take my meaning. I guess it all depends on how bad you want to do it. And on how much money you want to spend too.

Me

2nd thing If your going to go thru all that. The 305 isn't much more than the 4.3 for power or economy.

For all the trouble go to a 350.:)

that will make you smile.

I have a 94 with a 4.3.Would it be just as hard to put a 350 in my truck even though its an older model and doesnt have all the electrical components as the 98 model?

Yes..this gets asked a LOT...the only feasible way is to have a wrecked truck or something to take everything..'
fuel pump
ecm
wire harness
exhaust
mounts
rad
shrouds

and thats IF you have a complete engine,with a tbi,intake,brackets,sensors,etc

thats why the 305 to the 350 is an easier change :D

If you want to do a V8 swap go with a 350 because the 305 isnt a much of power increase over a 4.3 but you will need to replace almost everything in the engine compartment and youre gonna need a new exhaust, and drivetrain.

It's never worth the trouble to do an engine swap newer vehicles..... Only excuse for that is hotrods/musclecars... and Civics...