I want to buy an rx8 because I really like the body style of it but I would like to drop in an old mopar 360. The only question is if the car is an obd2 car with a non obd engine like a 80s model one how will I be able to pass emissions. Sorry if this is a noob or annoying question.

 

As long as the catalytic converter is in good shape, it will pass emissions without issue. Generally with used examples they are pretty trashed or completely removed. Dont let this turn you off though. You can get a cheap Magnaflow cat to swap in just for emissions testing then swap a midpipe in when done. Best way to do it.

I would also recommend reading the new owners sticky. Lots of great information in there.

edit: hope you have a large budget. This car is not easy to engine swap. Better off keeping the stock engine it's fine. Just get it compression tested before purchasing. Or if you want more power do a 13b-REW swap. The car is balanced around the rotary engine. Using a heavier engine throws everything off. You will improve straight line speed but sacrifice handling and overall drivability.

 

It depends, do you want the stock dash to work? Do you want air conditioning? ABS? If you start disabling computer parts, there are no guarantees anything would work. Emissions will be the least of your concerns.

 

It depends, some states only do Visual Inspections, if you have your cat chamber there (even if gutted), you will most likely be fine.

For sniffer you may fail, depends on how well it is tuned, but I'd say it it hard.
For OBD, it depends on your ECU, if it does not support OBD2, they probably will ask you to go through sniffer test. If it supports OBD and gives "Complete" reading all the time it would be awesome.
For stock RX8, some report by disabling the CEL the readniess monitor will become ready.

I am not familiar with emission as my county does not require it. Well yeah, you can move to a county that does not require it.