are you planning changing the engine box prop diff and driveshafts ?
If it is a major rebuild then at very least it will involve new engine mounts / mounting plates on the chassis, new gearbox mount, new prop, new diff mounts, is the diff mounted on its original arms if so then to keep from re building the diff frames then you would need a bespoke set of uprights .
I guess you could keep the diff/rear end as is and get a hybrid prop shaft made up.
If going type 9 on ford engine then there should be enough room in the tunnel
if trying to put a ford engine onto a mazda gearbox then I'm sorry I don't know although this site may help
http://www.p9cyoplates.co.uk/products
Do you mind me asking why you are going mx5 to ford?
I have a mk2.5 vvt 1.8 mx5 supercharged engine and to be honest I am really happy with it
good luck Gary