Isn't the 1300 a dual relief case? My engine is a restamped F125 engine with overhaul stamp in front of number. It is a single relief case. 69X77 is swept area, makes it a 1300? Mebe engine was rebuilt/stamped with an older case?

The 1300 "F" cases are definitely not dual relief cases. All 1960's 1300 "F" cases and 1500 "H" cases, as well as the various Type 3 cases, "I" etc, are all just modified 40 horsepower cases. They are single relief, have bad oil flow, small oil pickups, tiny oil pumps and are almost all cracked behind the flywheel into No3 cylinder hole. Stay away from them if you want to build anything but a stock engine.
The number "F125" was used only for Country Buggies. If you've got one, and it's not cracked, build a standard engine for your CB and you can say it's "original".
Recently I bought an "AB" case. It's from a 1300 standard beetle from the early 70's. It has dual relief, 1600 sized barrel holes, and would have had twin port heads. If you want to have a true 1300 case for your CB, perhaps for club rego or something, then that's the way to go, but they're not easy to find.
Cheers
Tony