1996 Chevy Silverado no fire at plugs vary weak at coil

Hello I use to have a 97 silverado it was totaled but still drivable. I bought a 96 silverado that run but knocked bad. So i took and switched motor and transmission all together wire harness an all. Hooked it all back up no start. It has a weak spark at coil but has no spark at plugs. One thing that I might of messed up was the set of wires that go into fire wall under AC drier I cut and resoldered with shrink tube vary nicely the wires matched up good. The only other thing that might be of help is the motor set for a year in my shed. Can you help