Your not crazy - its been done but it's all about money and how experienced you are. The FJ guys are slamming 4BJ and 223 into their iron all the time - but not without some hear aches. If you are just going to play with BIO D or SVO/WVO I would seriously consider buying a used diesel rig AOT fabing your Trooper. I see you are in the South as well, there are quite a nice ones out there.

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