Imperial mark II bottom bracket

hello fellow cyclists,

i was wondering if anyone has swapped or upgraded a stock BB to a newer style BB in an older style CCM.

i was given a an old imperial mark II, from the serial number im assuming it is a 1963... (if anyone can shed more insight on determining the age that would be great).... and the BB is a little rough. i plan to upgrade and i would take measurements and determine the BB shell width but its in my shed which is buried in snow. my plan is to order the parts now so i can have it all swapped before biking season is here. from what ive read the BB is a threaded english style BB, but if im wrong im hoping sumone can let me know.

can sumone can fill me in on an appropriate shell width and spindle length to have a proper chainline. your shared knowledge and experience will be greatly appreciated

happy riding