Good one Jeff. I have the same kit which, eventually, will be made as a 'H' model, in a diorama setting.
The info Wojtek has supplied is basically correct, but sorting out the detail differences can be a potential minefield, as each factory had slight differences, including the pattern of the paint scheme, and these changes were compounded by 'Block number' mods, as well as field mods etc.
Also, depending on specific period, the ball turret might be omitted, waist windows differed, etc etc.
There is an excellent reference book, which Glenn (T-Bolt) made me wise to, which explains, in detail, all of the various combinations, and it's well worth obtaining a copy, before you start work, as this will certainly clarify, and simplify, what's required.
The kit is, basically, a late model 'J', with a configuration that was relatively rare for any 8th AF crate before late 1944, but mods are fairly straightforward, and may include the use of vac-form transparent parts for the bombardiers glazing, main canopy etc.
The book is entitled "Consolidated Mess" - (there's a clue to the problem!!) - by Alan Griffith, published by MMP Books.
When I get a chance to check-out your subject, I might be able to offer more info, and possibly Glenn will also chip in, but, meanwhile, I strongly recommend getting that book (it's A4 format, softback, and not too expensive), as, if nothing else, it'll be a very interesting read.