Will a GEN III Hemi fit into a 71 Demon engine bay? Will stock suspension work?

Only maintenance I’ve done is oil change and plugs. It is no difference than any other engine for the most part. More room to work than in new vehicles. As far as fitting it depends on what year and what the motor is out of. I have a truck motor and the accessories are all up top ie: alternator compressor. The car motors are at the bottom and a few small cuts have to be made. The biggest problem is what transmission you use. I have a 2005 ram 5.7 and transmission with factory ECM. THE HOTWIRE harness is unbeatable the trans tunnel required cutting as the trans is enormous. You will have to do extensive research on what combo you want and ease of control and install. The New Hemi Swap forum is the only place you find out. There are guys who have done every combo in there. You just have to figure out what is best for your son. It will be confusing at first. But if you don’t research it right he would blow a bunch of money. He will need the basics; fuel delivery, headers engine control, new driveshaft, oil pan. I did the most efficient way for me I could. Used motor and trans from a truck $2500 (this was 2009)
Harness $1000
Headers $800
Fuel tank w/fuel cell 800
Shifter $175
Electric fan $150
Radiator $180 (Dillans Radiators)
Motor mounts ?
Fuel lines ?
Trans cooler ?
ECM $75

Labor - free (sleepless nights drunkenness, anger issues, depression)
There’s still quite a lot I’m sure I left out.