The KRTT, KHRTT, and Sportster XLRTT seat is the "long" race seat 52001-40R which first appears on the 1940 WRTT and continues through 1969.
The kit with everything necessary for installation on a K or XL including the seat is 52000-52R.
This seat is used on KRTT, KHRTT, and Sportster XLRTTs with both the small and large (non road racing) gas tanks.
The KR "short" track racing seat is 52001-48R which first appears on the 1948 WR and continues through 1969.
The kit with everything necessary for installation on a K or XL including the seat is 52001-52R.
This seat is used on the KR dirt trackers with both the small and large (non road racing gas) tanks.
This -48R seat is also use on the KRTT when the large road race 5 gallon and larger gas tanks are used.
Some factory team Sportster XLRTTs also used the -48R seat
KRTT, KHRTT, and XLRTT motorcycles also appear in Pohlman studio photos with the standard K and XL solo seats.
There is also a Daytona hump back seat 52001-53R for use with the large road race gas tanks.
There are also 1966 and 1968 fiberglass seats for the KRTTs.
Please consider adding this information to the technical "seats" section.