Man, I love it when I get one over on knepptune. I will mark this day down, and remember it with fondness.
The 750's are a bigger rt. They use the wider rt carrier (11' vs10'), double boom lift cylinders, and the heavier boom. They are probably most like the older series tms 760's (which had a little longer boom),they still had dash levers for controls and the old cabs too, up to the late 90's early 2000's.
The 730/ 740's have the 110' boom with the single lift cylinder just like the 700 series truck cranes. With the newer cabs, pilot hydraulics, and a little lighter boom.
The tms640 truck cranes with 105' main had a corresponding RT, it was the 640 rt, but they called it the "C" model in the rt, with the 105' boom and the smaller jib (both 640's jib's are only 29' retracted the main boom isn't long enough for the 32'-34' jibs. The 700 series jibs are longer, they have more main to hang it on.
Interestingly enough, there are places in the charts, where a 640 rt will outpick a 740rt, the 105' boom is lighter than the 110' and it gets a little more chart because of that.
But the 750's in the rt's are the last of the old school heavy boom groves, with the old control style.
You've been working too long on that new stuff knepptune- GMK, potain, and all that other oddball stuff.