1973 Scamp Rearend question

Hey Folks,

I picked up a 73 scamp a little while ago, and am slowly turning it into a beast. It has a 318 with 340 crank/rods, 360 heads. Just had the trans rebuilt.

However it has the stock one wheel peeling rear end w 2.76 gears. I want to get a limited slip posi with either 3.55 or 3.73 gears but have no idea where to start. I've taken it to a few shops and nobody can give me an answer on what size rear end it is. What did the 73 scamps have ? And what do I need to look for to get a limited slip 3.55 or 3.73… I've been researching online, but can't seem to find an answer. There's a ton of options on ebay.

Thanks!