i have 2 issues with my truck, first it idles rough, and second at 75-85 kmph, it stumbles/misses,only under very light accel,and then clears up after 85kmph. i have replaced the fuel pump,cap,rotor,wires,plugs,iac sensor. the truck has a aftermarket propane system on it. there is a black box that ties into the factory harness,its for switching from propane to gas,truck will not run with it unpluged. also it will not idle on propane. has anyone had these issues?
i do have a 94 318 magnum complete with harness,flexplate,torque converter,everything. i wanna put the 318 into my truck,its a 360 magnum . will the 318 drop in with minor changes? and will it bolt up to the bellhousing?

 

replace your IAC and EGR and the smooth idle and stumbles/misses should go away.

 

TPS sensor could be sticking or messed up some.

I've heard about a lot of people running propane in their vehicles (4 wheeling community) but I'm not to familiar with it myself to give input on it.

 

Yep, check tps at idle, IAC for sure... Also check primary and seconday voltage of coil and resistance in wire. Open pcv or leaking (and notorius ) plenum gasket

Its not a direct swap. Your 360 is externally balance with weight in the front and on the TC or flex. It also has a different cam..

Can it be done, SURE!!! But I don't think your problem is in the rotating assembly....

Im not a propane guy so hopefully someone else will chime in..

 

it wouldnt be cost effective or worth the power loss to swap the motor.