Hi, I'm building the 1/35 Tamiya M4A3E2 Jumbo and am using the turret that came with the kit. I am beefing up the turret and trans housings and hope to do a good enough job so it looks like an actual 'Jumbo' turret.

Are there any side by side photos or drawings of a jumbo turret compared to a T23?

I just don't want to build a T23 equipped Sherman later and find that my 'Jumbo' is undersized.

Steve Zaloga's article in the British "Military Modelling Magazine" a few years back was pretty comprehensive, if you can chase it down. Maybe someone could send you a scan (lost my copy in my last move--sorry).
Or, you could just buy the excellent Asuka (formerly Tasca) kit, which was reissued recently.

Military Modelling Magazine, "Silver Star Jumbo," Steven Zaloga, Vol 32 No 4 -- is the article you want to track down. Or you can see if there are any serious Sherman modelers who have stashed away (and never to be used) resin replacement Jumbo turrets. It's a strong likelihood that those guys will have gotten the excellent Asuka kit so no longer want their resin upgraded turret or transmission covers. You should put a "WANTED" ad up on the Armorama, Track-Link and Missing-Lynx classified pages.

Here's an article that can also be of help:
http://www.usarmymodels.com/MANUFACTURERS/Tamiya/tamiya35139.html

Classified pages
Armorama: https://armorama.kitmaker.net/modules.php?op=modload&name=SquawkBox&file=index&req=viewforum&forum_id=3&page=1
Missing Lynx: http://www.network54.com/Forum/47214
Track Link: http://www.track-link.com/forums/classifieds_private

Thanks for the replies and tips!

http://nadhi.blog63.fc2.com/blog-entry-368.html

I came across this link which had a good variety of different 'Jumbo' turret brands. I assume it's okay to link threads from other sites here, if not let me know.