I'm not sure if you've had work done at a machine shop as of late, but their prices have outstretched their usefulness. If you had your own mill and also had the expertise then I'd say go for it. I had a Series One 20 inch Model 45 bearing carrier TIG welded as it was cracked when I got the machine and then had the bearing size re-milled out afterwards to perfection and that was $60 at mates rates.
I would most definitely stay with the Briggs replacement as you won't have to mess around with changing any drive train gear and the extra cost involved. The Briggs engines are available in both 5/8 and 3/4 size PTO shafts and are the same costing for either.
Now as far as oil goes, Briggs have organised me a replacement motor as they can see the issue of what's happened.
All they really need to do now is actually clearly label either the packing carton or the engine itself that it requires oil as they've had a few issues as of late with some engines having a full crankcase while others only have around 150ml of assembly oil inside. They admit that a standard of some sort should be sorted out, thus why I got caught out like I did.
I will say that most manufacturers that sell new engines place predominant labels on their product stating "REQUIRES OIL". They do this so as to avoid having to ship engines as DG cargo (Dangerous Goods), so isn't a truckfull of engines all with 150ml of oil inside each one considered DG ???
So in the future "I ain't fallin for no banana in my tailpipe"
I live a 24 Hour lifestyle, but every now and again I seem to fall asleep, well at least that's what my wife tells me.