Ford ⇐ PSA (Peugeot) XD Series ⇐ Indenor XDP Range
(1972?-2003?)
The Ford-PSA-Peugeot XD series of diesel engines was sourced by Ford from Indenor through PSA Group’s PSA PowerTrain (Formerly Peugeot Citroën Moteurs). PSA had marketed the XDs very successfully to power several brands of generators, tractors, light trucks and automobiles including their own very popular Peugeot 504 series of vehicles (with XD90). In turn, Ford not only used these engines in their own vehicles such as the European Ford Granada, but Ford also supplied these engines to its subsidiaries, including Jaguar, Volvo, and Land Rover. Ford also supplied these engines through Ford Power Products to DNT, Lehman, Stratos, Vetus, and Volvo Penta where they were marinized.

Lehman 4D61 marinized from PSA (Peugeot) XD90 diesel engine like used in the Peugeot 504 automobile.
The XDs came in several 4 cylinder inline Displacements including 1.9L, 2.1L & 2.5L. The 1.9L had a bore of 88mm and was designated the XD88. The base engine for the marinized Volvo Penta MD21A, the 2.1L (2112cc) XD90 had a bore of 90mm. Indenor, who designed this series used slightly different model designations in their production, the XDP 4/88 & XDP 4/90 respectively. The 2.5L engine retained the same stroke as the XD90 but gained a larger bore of 93mm. The XD engines were also produced in six-cylinder inline versions like the XDP 6/90 which was used as the base engine for the Volvo Penta MD31. All these engines came in several versions depending on their application (Agriculture, Automotive, Industrial & Power generation) each with its own rating. Due to the popularity and commonality of these engines, most parts are readily available from numerous sources, including the various OEM’s where they were fitted into tractors, generators, light trucks, automobiles, and boats.
I've always wondered why Lehman originally turned to the Peugeot engine? Well, according to this, they were being sourced by Ford, who used the same engine in other products in their line. So in a way, they were just using another Ford engine, though this model was actuly built in France by Peugeot. That list gives us clues for more places to look for parts as well.