[BruceLambo]

Mark, the 369 came out in the Renault 20 and 30 models. You will have to count the teeth on the crownwheel and pinion to see what ratio you have. More likely you will have the 3.89 R30 model. Yes, you can have a new input shaft fitted, they just 'slide' into place. I made up a spigot bearing and pressed it into the crank out of a block of bronze, works fine. The 369 model has a 4-spider diff unit, whereas the R21Turbo etc dont, only a 2-spider unit (the V6's do etc) You can adapt one to go into your UN1 XX box with a small adapter plate. Check out the photo below. As for changing the ratios, you will have to go the path of a new 1-peice shaft unless he is going to weld on gear billets and machine them. Check my photo attached with a 1-peice shaft and the 369 4-spider diff in a UN1-13 box. It also has revised ratios based on the machine and weld technique.