We had all of the above. 1986 6.9 IDI, and a few 460's, and 7.3 PS, etc. They all needed work. The 6.9/7.3 are weak AF, especially compared to modern engines. IMO, if you want reliable, move up to a 2002/2003.5 7.3 PS. Best engine before tech got really burdensome. Only 20 years old plus a...