5.3l lm7 85 silverado

[2012LM7]

Newbee here. I am an old man that has been building old cars and trucks all of my life. I have always delt with the small and big block chevy engines. Now I am going into a different approch. I am going to install a 5.3L LM7 with 4L60E into my old 85 Silverado that I am restoring. I have not been introduced to the ls engines. My question is: can I put a Comp Thumper cam in this engine without changing the valve springs, pushrods or Converter? I also want to know how to hook up the starter,electric gauges, air condition compressor, and the electronic speedometer? In other words combinding the two wiring harness together. I have been surfing all of the forums between this site, Performance Trucks, and LS1Tech and have not seen any info on this, just the wiring of the 5.3L. Can anyone help with the swap? Thanks.

[screaminchicken]

Welcome! The valve springs and pushrods wont handle the amount of lift of the thumpr cam. You could run a stock converter but it would be an absolute dog, I would do a 3200 stall or higher. The starter wires up just like any other Chevy V8 pretty much. The speedometer can wire up to the VSS on the back of the 4l60e. Good luck!

[ccreddell]

The speedo on the 85 is mechanical if Im not mistaken. So it wont hook up to the VSS. What will work though, is to snag an instrument cluster off of a 88-90 suburban/blazer/crewcab. They have electronic speedos and its all down hill from there.

[94_OBS]

Any update?