What would it take to convert a schumacher laydown to the ST stadium truck? Arms, axles, and body?

Arms, axles, turnbuckles, body mounts, body for sure. Depends if you're wanting to run the buggy shocks. Otherwise, shocks and shock towers also.

Ah good point I didn't think of turnbuckles. I have a spare chassis so I'm hoping I can convert it

The chassis will be about 5mm too short from the ST chassis. Will have ridiculous amount of steering. Will need St rear towers on the conversion. Rear buggy towers have too much lean for a stadium truck.

I priced it out, buying the bits to do a swap is unrealistic assuming I can find a roller for $150. So I guess now I wait for one to show up for sale