Sure, you may have to change alternators. Check Small Engine Warehouse Tulsa Small Engine some of those places have replacement charts.

As far as physical size, crankshaft size, they are the same.

Walt Conner

I would go to the B&S website and download the IPL's for the 2 engines.
Verify that they use the same crank.
An alternator system can be swapped from the old engine, if necessary, at least on the 1st choice you offered. Verify that the "G" engine uses the same componants. MOST LIKELT it does.

A 31H777-0606-E2 isn't listed in the BRIGGS MANUAL, BUT A 31H777-0605-E2 is.

Details are important!

The basic series are the same and cranks and charging systems are interchanable.
The thing is, the same model may have a 1/2 dozen different cranks, depending on the PTO "stub" dimensions.

The main thing is to match the crank. IFthe replacement engine has a different charge system, swapping the flywheel & alternator is relatively simple

That is a good thing to check however, after rebuilding, assembling dozens of these engines from miscellaneous parts, I have yet to find one that didn't have a 1" X 3-5/32(?) crankshaft, std. to most B&S engines for some years now.

Walt Conner

Yup, pretty standard crank. The biggest differences are charging system and whether or not it has a fuel pump.