replacement engine 10" bolt circle vertical shaft

[1 FMF]

had an issue with my riding mower, carb let gas leak down from the tank and filled crankcase with gas. over a quart of gas. I started it and it ran for a couple seconds and didn't sound to good. Drained crankcase and refilled with oil, started right up but was blowing smoke near the exhaust. I think i maybe only blew the head gasket, and have the head off it now and it looked like the gasket failed. but I snapped 4 of the head bolts, will try drilling them later this week.
Any advice to drilling/removing them appreciated, have the engine on my bench.
In the event damage is more than head gasket, where can I get a replacement motor? Would prefer an OHV engine. Current engine is briggs 12.5hp, model 28T707, type 1113-E1, code 970718ZA. I think I can get the pulley off the motor to run the transaxle, which is all I'm using the mower for. the cutting deck is removed. current engine has a 10" bolt circle, having trouble finding engines that size. It seems vertical shaft lawnmower engines have 8" bolt circle, the bigger engines say 10+hp seem to have 10" bolt circle. I would be ok with a smaller engine, right now I could go up my driveway which is steep in 5th gear at idle with the motor barely bogging, so I don't need anywhere 12hp for what I want to do.

 

[Donald]

Irwin sells a kit with a few EZ-out bits and some left handed drill bits. Its on Amazon for $30 if I remember.

Have you looked at the HF engines?

A good welder can help new bolts to the ones that snapped and get the snapped ones out that way.

Don't snap the EZ-out.

 

[Rand]

all of harbor freights larger engines are horizontal shaft..
the only vertical ones are aprox 6hp and less.