Hello, and welcome!

I am just going to key off a word you used - inexpensive. No anytime you do a conversion there is considerable amount of time and money involved in getting everything to work right. If you have a thick wallet you can do anything. If you are on a budget pick up a decent used Trooper or if Bio Diesel is the main interest pick up a Benz W123.

86 Isuzu Trooper TD 5 speed
82 Isuzu Diesel I-Mark
86 300 SDL MB 126
85 300SD MB 126
82 300 D MB 123