A Texas-pattern D300 was used ONLY on the 1980 IH Scout II.
I haven't seen one for sale for less than $750 in many years; usually they are into the 4-digit range on the rare occasion you can find one for sale...
The T150 bell will work, plenty of info out on the web on that. If the Ford T18 you have uses a 6.5" input shaft, you may not need to swap input shafts.
As Dempsey said, PartsMike is a great source for info and all parts needed for your swap.
Here is some good info related to the T18 swap:
Swapping T-18 into your Jeep
Good luck, keep us posted on your progress.