RX-7 LSD conversion help

I'm doing an RX-7 LSD swap in my garage, and I was wondering if anybody knew the width of the pin in the stock diff that the spider gears run on. It also acts as an axle stop, so you can set the axle bearing pre-load. The LSD (out of an FC RX-7) is open all the way through, so the axles have no stop pin. I need to machine a spacer to go in, but I was an idiot and gave away the stock rear end before I had a chance to measure the pin diameter. Once I make it, I will heat treat it so it doesn't wear out in a month. Here is a pic of what I'm talking about:


I have read of people welding washers to the ends of the axles, but that would take quite a few to get the right spacing, and they seem like they would wear out since most washers are made of crap steel.

I bookmarked a link where the guy added 3.5mm to each axle end.
One side he welded washers, the other side he just kept layering a weld bead until he reached 3.5mm.

Thanks for the info. From what I read, his diff (and many people's RX-7 LSDs here) still have a pin in the center, it's just narrower. Mine is completely missing. He said that the stock pin in his was about 20 MM in Diameter. Maybe I'll machine that lengthe first, and see how it all works out. It's a little weird in the sense that my axles will actually be pre-loading off of eachother instead of the diff pin, but it's probably fine......Right?