Need some info on a 413 that I found

I found a 413 that is in a old Chrysler and I jotted down the casting #'s of the engine. Can one of you Mopar experts help me decipher exactly what this engine is?

Casting #'s as follow;

Drivers side of block- 1851629-7 R.L. 1961?

Flat machined area by the distributor- MP4I3 I74I2 (the "I" may be 1's)

Driver's side exhaust manifold- 1739800 ( the 8 may be a 3, i couldnt read it very good)

 

Btt

 

1961 rb 413

 

Typically part numbers do not include the letter "I" or "O"...for future reference. This doesn't apply 100% of the time, but it is an unwritten rule.