Thanks to Nelson Bove and George Krem and others, I carefully researched and updated the R3 listings last year.
Engines A-1 through A-10 were built.
B1- Dismantled by Paxton 1963
B2- Dismantled by Paxton 1963
B3- Dismantled by Paxton 1963
B4- Exists from a convertible, Texas 2002
B5- Installed in R1722 as of 2010, Paxton sold in 1967, may be 299 cu. in.
B6- Installed in R5386, as of 2011, from South Bend Technical School
B7- No information
B8- R4 engine only, Bonneville #3, parted out, heads saved as of 2000
B9- R4 Lark Convertible Bonneville #3, 299 cu.in. from Paxton August 1963
B10- R3S H320, R5089. 1st production R3, 4-speed
"B" numbers at the end skip around, seem pretty consistent thru B117, then B130, B153, B299 and B300. If all numbers through B117 were used we have 131 engines.
Remember this is what I have been able to research, more info will be appreciated.