The original 1940 Special motor that you reference had a top end similar to the '41 WR. The difference is that the special angled lifter bases are set up for roller lifters with the rollers ground at the proper angles to mate up with standard WLDR cams. The bottom end was produced in both roller bearing/bushing configeration and in all ball bearing configeration. Dale at WTT has several of the all ball bearing versions. I don't know of any literature that references the all ball bearing version, but I know they exist. I have seen the literature that describes the 1940 WLDR with Valves Close To The Bore and the unusual lifters and bases. The literature also shows that the 1939 WLDR used a "Baby Bosch" racing magneto and the 1940 WLDR used an Edison Splitdorf magneto.