B3 - B4 rear subframe easy to spot difference ?

[Marco Weibel]

I am about to look at a rear subframe to replace the rotten unit on my B3 89 90q20V.
Is there something visible to distinguish the two from each other ?
A lister mentioned different suspension geometry on B4's and are therefor not interchangeable.
A tell-tale sign to distinguish that what I am buying is a B3 sub ?
I just want to make sure... the seller seems fair tho but ... you never know !

Thank you for your input.
 MW

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