If you are serious about two hosers the following issues of HDS magazine are MUST READS IMO....
Volume 11, Issue 1 Number 34
Volume 11, Issue 4 Number 37
Volume 13, Issue 1 Number 42
Extensive background on everything from serial numbers and production dates to what and why they did it the way they did it.
http://www.hds.org/ You can join and order back issues here.