The only engine parts they share is the fuel filter housing and radiator, nothing else will fit, oh air filter element, thats it.
They are talking absolute rubbish, get them logged on to here

I would make an interesting thread
Why is the engine going to fall out

the car will rot away before engine mounts rot, unless they have been fiddling with the mounts that shouldnt be an issue, pop your head down for a look, bet its fine and they are being nasty, as you cant look after engine mounts and bolts seized tells me those bits havent broke before so you would expect them to be seized or round off as its on old car, they should be prepared for that.
Out of curiosity how is the rest of the car for rust ?