Bill. The Dual Range hydro was first introduced in 1952 and remained the same until revised for 1956 as per 80 years of Cadillac lasalle by Mc CaLL, thus your 53 hydro should be a direct swap into a 52 with zero problems.
The April 1977 Self Starter mag has an interesting article for 49 buffs whom might be considering this conversion as follows:
Installing a 1952 Dual range Hydramatic in 1949 models by Bill Woodman Northrop Colorado.
One of the biggest improvments in the 1952 models was utilization of a revised hydramatic which incorporated the hydraulically applied reverse (to permit rocking of the car) from the 50 and 51 models and a change which allowed selection of 3rd and 4th gear for normal driving. I felt those advantages warranted use of the "Dual-Range" over rebuilding the "49 unit. On the other hand, I wanted to use the stock shifter mechanism-trannt mounts, etc. Let me say here that it all worked outperfectly. However, there are some minor mods.
1. All engine bolts and rear mount locations-same.
2. Use the 49 driveshaft including front yoke.
3. Gear shift linkage,indicator etc, work fine.
4.Use the 49 oil pan and dipstick. Slight grinding of the of the servo casting or re-denting side of pan may be necessary.
5. The throttle pressure rod from the carb will have to be slightly re-bent to clear the shifter arm (coming out of the steering column).
6. Speedometer gear (52) correct for 49.
Enjoy
Jeff 49 fastback :<)
