On the subject of NOS Briggs engines I have a few.
One is a 3-1/2hp 92900 series push mower engine, it's that cool bronze color. Made in 1974. I have a perfect mower deck for it. I actually wouldn't mind finding a NOS or very nice sycamore or Kmart deck and handle from the same era for it. Maybe a snapper?
I also have a 80000 series 3hp horizontal. Heavy duty version with ball bearing in pto side.
I did swap the crank as the one that came with it is a weird external threaded one and shouldered, the last inch or so is cut down to ~1/2". Never fired since built in 1970.
I had what I thought was a low hour similar engine here but was missing a few things. So I pirated the crank out of it and just finished swapping it out as it is a straight crank with 3/4" diam and full keyway, internal threaded 5/16 fine. It miked out exactly the same as the weird crank that this engine came with on the rod journal. I did pull the bearing off the new crank and pressed it onto the replacement Crank. I did spray the crank journal and cam bearing surfaces with some spray white lube as I put it back together. And I pulled it over once reassembled and it does have a nice bright blue spark. I didn't put anything flammable in the carb or spark plug hole as I still didn't put any oil into it.
I also have an nos 8hp vertical from (I think) 1984. I have a 40" swisher tow behind that is recieving that one. That machine originally had an 8hp Briggs that has blown a rod for the 2nd time according to the PO.
I also have a 12hp I/C, 1988 electric start model. it just turned 7 hours on the mighty tach/hour meter on my new to me Bobcat commercial 32" walk behind mower. I put that one together late last mowing season. I wrote about that one here as I was putting it together. That one ain't leaving.
I also have a late 80s 4hp I/C push mower engine. I also have a purpose for that one. You guys see my wanted ad for a chute extension for a bobcat 21" push mower? I have 2 of them, one is getting this engine.
I also have 2 brand new never fired Tecumseh LAV35's. Real short crank, vertical pull start. Spec numbers 1 digit off from each other, one 1969 the other 1970. Factory replacement for the old toro Guardian/Whirlwind push mowers.
And 1 more. Tec HM80. Was set up for a minibike or go cart type throttle, I had to change that out to a different style for the tiller that I put that one onto. That tiller went to CL earlier today, no bites yet.
All of these except for the 4hp Briggs and the HM80 came from 1 guy. A retired rental yard mechanic who was cleaning out his garage prepping for a move South.
The 4hp came a year earlier from an auction that I went to.
And I had to drive down by Comiskey park (where the white Sox play their home games) for the HM80. As with the rental yard bunch, I found the HM80 on CL. And went after that one just for this tiller. He had started it one time just to hear it run and then stashed it under the bench, late 70s engine he bought new with a purpose for back then that didn't happen. I did wind up having to replace that nearly new carb, all the soaking in the world didn't work. I found an nos one on eBay that wasn't an arm and a leg.
I have maybe another 1/2 hour of run time on that one. Judging by how clean the cylinder is and the intake port is, and the paint barely being tarnished on it's muffler it can't possibly have more than an hour on it from new.
On the rental yard bunch, I went there hoping to buy 2 of those but got a "all or none" spiel when I got there.