Which alternator for 3.5 v8

Hi all

Wonder if someone can help.
I've rebuilt and fitted a v8 3.5 to my Series 2a but it looks like the alternator is on its way out. It is making an intemitant screeching noise that is defintely not the belt. I bought it new from Rimmers bros about 12 months ago but as there wasn't one on the old motor I wasn't sure I'd bought the right one.
This is the one I bought:
https://www.rimmerbros.co.uk/Item--i-STC234P

My mate who fitted it told me he had to switch the case round to get it to fit (the one I bought is RH).
Anyone know which one I need. I bought a right hand one thinking it would work but it looks like I may need a LH version? The engine is a early 80s 3.5 without aircon or power steering fitted to a series (as per photos).

Any advice appreciated part numbers would be really appreciated.

Thanks
Alex

The 3.5 RR with carburettors had either RTC 5845 or RTC 5680 fitted according to my parts book, both were the standard A127/65amp.
The parts book doesn't show the side but the Haynes manual shows it on the left /drivers side.