'60's 1500 Series Truck Questions/VIN listed

[MikeIIDC@domain.elided]

Well, after 12.5 hours driving around Northern CA looking at several
IH's that I have known about for some time, I have arrived home with a
few questions.
What exactly was the 1500 series made for in the 60's.  I had found one
that used to be a service truck for a towing/garage company, and went
back to look at it.  Right now it is simply sitting out in their lot, as
it has been for the last five-eight years.  It is in pretty good
condition as far as rust goes, but is, of course, faded.  I had
originally planned on checking into it as a parts truck for my wrecked
'68 T'all.  However, after checking it out, I am a little intrigued.
It currantly has a utility bed on it, but when I was looking at the ID
plate on the door, I could have sworn that it said WB: 156.  It did not
look that long.  Is this an optical illusion created by the utility
bed?  Knowing that my '68 T'all has a 110" WB, and the crewcabs I have
recently been lusting after  have 164" WB, this doesn't appear to be a
156" WB!  Perhaps they changed out the rear body?
This may be also, because it also said on that plate that it was rated
with a maximum GVW of 15,000 lbs!  Was this designed to be used as a
wrecker?  I can't imagine what you could put back there to need this
much support!
Regardless, once again, I am intrigued!  So if I got this, could I put a
regular bed on it?  Did they come in a size to fit this WB?  Also, it
has the BIG rim front tires (20" rims, maybe), like an old fire truck.
I kind of like this idea-makes the front stand up nice and tall.  The
owner of the garage assured me that this was a 4WD, but there was no TC
shifter that I saw anywhere.  Did IH make full-time 4WD for certain
uses?  Did they make them that rode on these taller tires?  Of course,
they also assured me that it had a 345 or 392 in it, and it has one of
the old straight 6 cylinder engines, though I don't know what size.  The
rear axle was a dually, of course, as I would imagine anything rated to
this weight would have to be.
I am assuming that it is not geared too highly, as it was probably made
with much more grunt than speed in mind, but could it be made into a
good tow rig?  I would think it would be ideal for this, if it would go
fast enough to get you anywhere!
So, to those of you with the knowledge, the information, and the books
with the info in them (I implore you, John Landry, Howard Pletcher, and
Scott Satterlund, among others), could you please look up the VIN and
tell me anything you could find out about this beast?

VIN:        SB341877C

I don't know the year, though they thought '64.  I was thinking that one
of the "7"s in the VIN meant it may be a '67.  It was definitely of the
'63-98/9 style.  Had the grille with the rectangles, but the bigger
ones, not the smaller ones like my '68.
Thanks to anyone that takes the time to help with this.

Michael