Unless you already have the Verlinden M50 turret in the stash, I would recommend passing on it. It's not particularly accurate, and the gun tube is all resin and warps if you look at it wrong.
As to what hulls you could find converted to M50: almost anything, but the composite hulls were particularly scarce. Not to say it didn't happen, but a pic of one would be hard to find, I'm thinking... Of course it's really hard to say "never" when talking about IDF Shermans.
Keep in mind the IDF had a fair amount of M4A4 hulls with the standard 75mm gun and preferred to convert them to M50, as the majority of the existing cast hull Shermans in inventory at the time were M4A1/76 HVSS, and the idea was to improve those tanks most in need of it. Since the 76mm gun in the latter was fairly potent with the right ammunition, the decision was apparently made to prioritize conversion of the older, less potent M4A4(T) with the 75mm gun.
In a strange way, this also accounts for the fact that most of the M51s were based off the M4A1/76 HVSS tanks.
A couple of sources for good M50 turrets are Greg Buechler and DEF Models. I have one of Greg's turrets and it's sweet. I plan on using it sometime soon, just not sure on exactly what hull yet. If you can find one of the old MP kits they're pretty good too. I built a welded-hull M50 using one a little while ago, with what I think are good results. I did have to scare up an aluminum gun tube, since the MP part had some nasty ejection pin marks in it.
Pic:
i1236.photobucket.com/.../SD530900_zps1125bebf.jpg
Shep's book has an M51 that he cobbled up from lots of bits, and considering the amount of info he had to go on at the time, it's an excellent model. There are a few IDF Shermans in Jim Wechsler's (sp?) "How-to" Sherman book, available from Kalmbach, that are well done, and this book is readily available and a very good source of ideas.
Edit: Whoops, forgot to use "rich formatting".... well,click on the link, should work.