Now I seen the pics Id stay with the flathead if not give it to me. I thought
it was a regular bus, for that, a regutlar F250 would do it thats not heavy.
We had many of those but around 40 or so passenger and the flatheads
worked perfectly. We had three Marmon Herringtons with V8 flatheads that
were city buses, they ran well and had one I remember with a 337 flathead.
I came from family owned bus co. I know my buses well

 

Frame swaps are NOT "easy", especially on an oddball vehicle like your bus. If you are not a highly experienced/skilled custom fabricator, you would be much better off working with the chassis that is already under the vehicle and modifying it however you'd like. You can add any type power anything far easier than trying to fit a different frame. The bonus builts are much narrower than any modern truck. That bus looks like it is on a shortened chassis, but that may be an optical illusion due to the shape of the body. Chip Foose updated a bonus built "short bus" (but not as short as yours!) for John Force on his Overhaulin TV program. You may be able to find videos of the show or more info on the net. If anyone could have done a frame swap and would have been easier or better to do Foose would have done it.

 

With a complete frame swap you get the best of both worlds. You get the updated suspension, engine, steering, brakes and handling where as putting everything under your frame you don.t know what you going to wind up with, just my opinion. I have done two frame swaps and both turned out awesome, Your going to get lots of different views on doing frame swaps so only you can decide, Garry

 

One of the main issues with a frame swap is usually the bed, but in this case I'm sure the floor is high enough to clear almost any kickup over the rear axle. No one has brought up the apparent widowmaker wheels, worth mentioning...

That is a unique way to pipe the flathead's dual water inlets/outlets, I'd be surprised if it works satisfactorily.

 

All 2 wheel drive ford f-350 f-450 the frame is almost Straight and 34 inch you would have move the rear axle forward

 

Sadly there is no ideal frame choice from a light duty Ford for the 48-52 trucks. It needs to have front steer or it will have an ugly steering setup. A maximum frame width of 34". Ford 2wds got front steer in 1980 and the last full length 34" frame was last used in 1979. While cab and chassis trucks after 1980 have the rear section 34" wide, the front is 37.5" which will cause many issues.

Best bet is to look at 80's to mid 90's medium duty trucks F-500/600/700 as they are 34" wide full length, front mounted power steering box, disc brakes and serviceable wheels.