MGB spigot bushing size question

[Jeremy DuBois <jer@thlogic.com>]

  Hi All,

        Just a quick question I hope somebody can answer.  Somewhere along
the way I lost the spigot bushing that fits in the back of the crankshaft on
my MGBs engine (no, no, not while driving it, while disassembling it :-) Not
a biggie, since I was going to replace it anyway, but I see that there are
two different ones to choose from, a 1" bushing and a 1 1/2" bushing. 
Anybody know what the reason for the difference is, and what I can do to
figure out which one I need (since I can't measure the old one)

                                        Thanks,

----
Jeremy DuBois                              jer@thlogic.com
Manager, Info Systems                      http://www.thlogic.com/~jer/
Thermalogic Corporation                    '60 TR3A, '74 MGB, '76 Spit