Front subframe differences??

[Bitsilly]

Can anyone sum up how front subframes differ?
I know it is a big ask, but any help would be appreciated.
I know the early ones have a single bolt top mounting, and they later became rubber bush mounted.
What I am really wondering is if the size of the cradle actually ever changed, and to what extent they are interchangeable.
I am getting serious about fitting an electric motor to my car, and if so it would need brackets welded onto the front subframe.
These could be cut off if the process is ever reversed, but I am thinking that it may be better to get another subframe altogether and put the old one aside.
If I do that, then I would like the biggest available space to play around in to fit a motor in the best position, hence the question.
Hope that makes sense!

[Bitsilly]

I have just gleaned that the auto subframes are wider at the bottom, I think!

[MrNoo]

The early frames were twin bolts or studs/nuts, two each tower, solid mounted onto the front panel and toe board.
Later ones were large single bolt in each tower and rubber mounted on front and toe board.
Guessing the last ones were single bolt.
Suspect the tower tops are pretty much identical bar the mounting method, 4 bots or two.

[GraemeC]

There have been all sorts of variations over the years:

Twin bolt, dry, manual
Twin bolt, dry, auto
Twin bolt, hydro, manual
Twin bolt, hydro, auto
Single bolt, manual
Single bolt, auto
Single bolt, manual, post '90 (not Mpi)
Single bolt, manual, MPi

Yes, the lower legs of the auto subframe give a slightly wider gap - approx 3/4". They also have the front cross member bowed forward slightly (as do the post '90 subframes)

[Bitsilly]

Thanks gents,
I will try to wrap my head around and process, and may then get back to you.
I did read somewhere that the toe board may need strengthening sometimes.
Many thanks

[GraemeC]

Later, single bolt subframes, which had the rubber rear mountings benefit from the toe board strengthening.
Which type of subframe you need is effectively dictated by what age your body shell is.