Most Toyota diesel has to be sourced from overseas for conversion purposes. The most common Toyota diesel engines that are used in conversions are the 6 cylinder variants offered from 1986-current which are the 12HT, 1HZ, 1HDT, 1HD-FT, and the computer-controlled 1HD-FTE.
12HT: The turbo version of the 2H. Excellent engine and quite powerful. Very limited production run 1985-1989
1HZ: 6 cylinders, naturally aspirated. Excellent engine and is seen as Toyota’s 3rd world workhorse engine. Production run: 1990-current This engine takes very well to an aftermarket turbo.
1HDT: The turbo version of the 1HZ. Excellent engine for an 80 series conversion. Available from 1990-1995
1HD-FT: The 24 valve version of the 1HDT. Excellent engine for an 80 series conversion. Available from 1995-1997
1HD-FTE: A computer-controlled version of Toyota’s 6 cylinder diesel. It started in 1998.
1JZ-GTE: The first generation 1JZ-GTE employs twin CT12A turbochargers arranged in parallel and blowing through a side-mount or front-mount air-to-air intercooler. The later second-generation engines had this problem fixed and in Japan, there was actually recall in order to repair the first generation engines, though that does not apply to 1JZs imported to other countries. The fix is simple, and involves the replacement of the PCV valve (2JZ); all parts are available through Toyota. The third generation of the 1JZ-GTE was introduced around 1996, still as a 2.5-liter turbo, but with Toyota's BEAMS architecture. This included a reworked head, a newly developed continuously variable valve timing mechanism (VVT-i), modified water jackets for improved cylinder cooling, and newly developed shims with a titanium nitride coating for reduced cam friction. The turbo setup changed from a parallel twin-turbo (CT12A x2) to a single turbo (CT15B).