Vintage RC10 project - chassis found!

I was checking out some vintage RC10's eBay last night and I came across one that looked like a good specimen for a project. I liked what I saw in the pictures, and the price was reasonable at $75.00:

It's not a 'complete' roller, but it is clean, and almost all the important parts are there. The one thing I'm having a hard time figuring out is the 'version' of this chassis. 

There is a stamp on the rear motor housing, just behind the six-speed transmission, seen below, but I can't make it out as an 'A' or an 'AB' or whatnot. Does anyone have an idea?  I looked on RC10talk.com, but I don't think the ad's pictures show enough detail to determine the correct model. 

The bottom is not drilled for the Stealth Transmission, so I'm pretty sure it's an earlier model, maybe a so-called 'Cadillac' chassis (so named for the address Associated Electrics moved to from their initial Edinger location.)

Further, the front suspension arms are of the 'trailing' variety, where the front axle is trailing behind the hinge point.  This is the original, narrow track design. 

I put in a bid and won; I should receive this roller (sans wheels, body & electronics) early next week. Not sure what the project will be; I could still go for a 'full' restoration, a rebuild with more modern parts, or even do a RC10T conversion. Any thoughts on which would be best for this platform??

Stay tuned for a status report and further rebuild/restoration/conversion updates!