Sounds like your wanting to drop in a BB. If so there's a few more things you'll need to change and that's the engine frame mounts and tweek the Trans cross member in case your unaware.
Yes the heater core is the same though the holes in the firewall are in a different location. Just drill new holes and plug up the others.
The wheels and roll bar both being vintage may make them difficult to find or pricey if you do. Only cause of those looking to restore a nostalgic drag car.
I have seen them out there but not the easiest to find. I'd suggest CL, swap meets or ebay as your best chances.
Btw...I hope your wanting roll bar for the nostalgic look and not relying on it's safety...just saying
Hope that helps