While this won't suffice for roscoe

, here’s more real world evidence that the design at least is real. Head gasket for 1HZ-T from toyota, no. 1 gauge, unique part number not shared with any other vehicle, which is actually the same thickness as the 1HZ no. 5 gauge. It came with the 1HZ-T rebuild kit which has the 1HZ-T pistons manufactured to toyota specs nowadays by diesel power parts from engines australia.
detail on the gaskets...
GHTO340G1/G3/G5 – head gasket to suit Toyota 1HZ-T
O.E. Number: 11115-17020-01, -03, -05
Construction: Steel laminate head gasket
Gasket Selection by Piston Protrusion:
0.475 - 0.525 mm 1 (340G1)
0.526 - 0.625 mm 3 (340G3)
0.626 - 0.725 mm 5 (340G5)
Gasket Thickness: (Grades 1, 2, 3, 4 & 5 used from factory, but only 1, 3 & 5 used for aftermarket.)
1.35 - 1.45 mm 1 (340G1)
1.40 - 1.50 mm 2 use 3
1.45 - 1.55 mm 3 (340G3)
1.50 - 1.60 mm 4 use 5
1.55 - 1.65 mm 5 (340G5)
Other evidence, I was having my hybrid 1HZ pump with 1HD-T compensator tuned the other day at an injector shop and when searching their database for pump ibench test specifications to guide the process, as well as the 1HZ and 1HD-T specs they also found published specs in the exact same format for the 10mm 1HZ-T pump on the 24v coaster, which didn't have a boost comp by the way.
I have copies of all three pump testing specs and was thinking of scanning them for karters 1HZT tuning thread, not for tuning the hybrids but its an interesting read for anyone who just wants to know the details of the 1HZ-T pump design specs by comparing the differences with the 1HZ and 1HD-T, which sort of tell 's you a little more about just how hard it was designed to go compared to the 1HD-T.
as for my 2 cents worth on its existence... I reckon one will turn up eventually if we can convince a few european brothers to invest (or waste) some (or heaps of) time to search wrecking yards... i mean in terms of one run of new untested 1hz-t coasters sold for just 2 years three months alongside the tested 1hz coasters.... there must have been less than a thousand sold i reckon, and think about it, we are talking about a bus, usually bought by the fleet owners accontant thinking about nothing more than upfront and running costs and passenger capacity, the bus driver wanting a little less ankle strain and overtaking stress would have rarely been the one deciding which model to buy, so if we assume they were produced, finding one now 20 years later will be a needle in a hay stack... there are like hundreds of landcruiser forums world wide and not a single coaster forum, so we'll need someone with access to toyota europe sale figures to settle the argument of whether one was assembled and sold
at the end of the day it's obvious the 1HZ-T was designed by toyota engineers and for those who just physically can't transplant a 1HD-T, its nice to know we can use these unique parts to make our own 1HZ-T's more reliable instead of just slapping a kit on and crossing your fingers!