As I may not have been clear, I do have a 38 block, but it is one of 2 (other is 49) i'm looking at to rebuild. I will not know which to use until it gets to the machine shop cleaned and inspected. Your block can be mended with a product called Jupiter B, welder does have to know how to use it. That said I would be interested in the crankshaft main caps and the bolts. If you get another block. These caps would go on my 1952 block which also has a crack (I assume your crack is right below cylinder deck) I will weld up my 1952 block if I can find some caps. If you can find a welder you can make a plate and gasket, block off the cylinder deck and pressure check the weld, any pin hole leaks found can then be touched up. Block needs to be preheated warmer the better, but peening the weld area as you go is the big part of it.
If you are a stickler for the early block look, 38 to 47 are close. 38 dipstick is not in the same location as the later blocks. I believe 40 up. Not sure about the 39. That said. the later blocks, the motor mount casting added can be ground down and bolt holes filled and painted. On the other hand the later blocks with side mount much smoother and dont get the oil leaks killing the mount. I dont think anyone would notice if you did the grind idea, except for the serial number. Most do not notice the 50-52 water pump elbow to side of block. I assume Buick did this to help with cooling because of the Dynaflow but so far no one I have talked to confirms this, nor read anywhere. Maybe some one can pitch in hear, I would love to know.
