Hi all. 1985 RX-7 ???'s

Found a good deal on an '85 RX-7 GSL claiming to have the original 12a motor in it, and was thinking that the 13b was the stock motor in these?
They also claim under 80K on the vehicle which is obviously intriguing. My main question is:
Which motor is the standard and what is a quick and easy way to tell which is installed?

2nd this will be my 2nd RX-7 I'd like to make this one hop and don't mind upgrading/ rebuilding motors. Is it advisable to supercharge or turbo charge these motors without updating seals etc, or can you more or less bolt a system on and just mind your P's and Q's on the boost levels?

I've been poring throught the FAQ much info to absorb, but well worth it!

Thanks!

Mike

Only the GSL-SE had a 13b for the 1st gens, everything else is a 12a to my knowledge.

I know that in Japan, mazda release a turbocharged 12a so you can go that route, but as with any n/a engine you should do internal upgrades if you plan on running serious boost.