Turret mantlet
 

I believe the Valentine turret mantle was used to mount the 2lb in early Ram's.
From photo's the Valentine mantle appears identical to Matilda mantle's.
Matilda's CS fitted with 3" howitzer appear to use same mantle as 2lb.
Would a RamCS with 3" howitzer not have been a rather simple development rather than placing Lee's/Grant's with Ram units.

I know New Zealand modified Valentines to Close Support tanks with 3" howitzer.