I've also done the newer car handle and latches on several cars & trucks. The new stuff pretty wide for an old, thin 30s door, I have added about 1/4" (you only need it for about 6" space right at the latch) to the inside of the old thin doors to accommodate the newer latches, it was well worth the extra work. I've used K Car stuff, 80s 5th Ave stuff, and my 48 has Dakota stuff in the doors. We are probably going to put Dakota latches in my sons 57 Dodge, because we have a driver door latch issue. With a little thought, you could use your existing handles with modern latches, if your handles are good.(I'll let you know if we go that way, but the car is on hold right now.

As far as that "Kit", 40lbs solenoids are borderline, I've seen kits with 70lbs solenoids, those would be OK, and have at least 1 door that can be opened if the electrical system is down (dead battery). Gene