here's a suggestion call marlins and ask him they have all the info you can stand
he is the man when it comes to toy transmissions
the 2wd isn't the same I don't think
I had a g52 in mine and broke four of them now it has a later model v6 trans in it
a r151f is an extremely strong transmission and will bolt right to your truck unless it is a v6
the w56
g58
g52
r151f
will all bolt up if it is a 4cyl
but the t cases are different on the r151f's the transfer case has a 23 spline input
some transmissions have the t-case shifter in the top of the t case
others have it in the tranny
called forward shift or top shift
so again call marlin's they can tell you what you have and what will fit and what can be made to fit
and what will be involved with each process
Go with a R151F if you can afford it. Be sure to get the bellhousing and Tcase along with the gearbox (all as a unit). The R151F requires a 23 spline input Tcase, and a different bellhousing than the G52/G54 or W56 uses.
@nd choice is Marlin's W56HD. It'll bolt to your G52 bellhousing and you need to ensure you get the correct Tcase shifter model to match your existing 21 spline Tcase.
JR