engine swap

Hi. Can get a mini panel (really rough and no engine/trans) fairly cheap. My brother has an Austin America with extra engine. I read somewhere that most of the Austin America's were crushed after donating their engines to minis. My question, will the Austin America 1200+ engine fit in any mini.. i.e. austin, morris, hillman etc.?

The Austin America 1275 engine/trans will fit a Mini with a bit of modest work. Don't recall the exact details (I did this 25 years ago) but I don't think it was that difficult. May have to play games with the shifter, exhaust and upper engine stabilizer to fit the Mini chassis. I'm not sure about the Mini halfshafts...they may bolt up to the America trans. Final drive ratio will be "off" since Minis have 10" wheels and the America was geared for 12" wheels. This combo will give very good low-end power, but very limited top speed (the 12" wheels will not fit the Mini...different bolt pattern). 13" Sprite/Midget wheels can be fit to a Mini, but they do not have the proper offset (backspacing).
Hillman is not built by BMC/Leyland and is not related to the Mini. Hillman is built by Rootes Group (and later Chrysler UK). Putting a front-wheel-drive Austin engine in a rear-wheel-drive Hillman would be a huge undertaking.

I am not an Austin America (AA)expert, however Minis came in 10, 12 and 13 inch rim flavors and the bolt patterns are all the same. I have a set of 10s and 12s for my Mini. I would be surprised if the AA rims did not fit. The van will, most likely be 10 inch with drum brakes all around and the AA will be 12 inch with disks up front. The 8 1/4 AA disks will not fit inside the 10 inch wheels, you will need 7 1/2 Cooper S disks for that. Unless you are fastidous about maintaining the drums on the Mini you will want the disks to keep up with the 1275 engine. If the van is early, it will have a "pudding stirer" shifter and an additional hole will be necessary to acomodate the AA remote style shift mechanism. You say the van is rough, so the extra hole probably isn't a problem (you might not want to patch THAT location in the floor). AA engines are routinley grafted into Minis. I believe AAs had a wet suspension; this is difficult to graft into a dry Mini. This leads me to think that most grafts consist of the AA engine and transmission being joined to the Mini at the half shafts.

ThomP has said it all, really. If it's an early Mini with 10" wheels you may want to swap the final drive otherwise it will buzz like heck - great for autocross etc but lousy on the road.
Driveshafts should bolt straight up with the proper couplings.
Regarding brakes - if the van has 2ls drums, in my view they are better than all others for 10' wheels, except maybe Cooper S, and they're not that much better. The old single-leading shoe brakes are not too good, though my wife drove a 1100-engined Mini with them for a few months without bother.
Making a hole for the remote gearchange is no problem.

Appreciate all the info. The panel was really really rough. Brother has about convinced me would be better served doing a restore on the AA. Will probably drive there this summer with a dolly or trailer and drag her home. Another project!! Woo Hoo!