Once had a Mini van. Great fun and quite capacious but very,very noisy. Had a friend who fitted a supercharger to his mini - it lasted 4 miles before the engine disintegrated - and another who put in a bored out 1400cc motor. That one went through front tyres in anything from 600/1000 miles!

One of the major things to check is the integrity of the rear sub-frame and its mounting points, also the sills. Major points for rust.