Well, more accurately I believe, the clearance was updated later. So not really a mistake, just a specification change. But yes, the TR2/3 workshop manual calls for 1.5 to 2.0 flats, which is too much.
There were several other changes over the years, most of which can be found in the later editions of "Practical Hints". Unfortunately I'm not very good at remembering them that way, but here's what I can think of offhand:
1) The later clutch slave mounting arrangement is not shown, and the Girling slave cylinder illustration (in the back) shows a spring that should not be there. The spec was 0.1" for freeplay at the Girling clutch slave (the workshop manual only gives the Lockheed spec of .075"). (However, I like to set mine even tighter, around 1/16", for a higher clutch pedal. Downside is the need for more frequent adjustment.)
2) The amount of grease for the rear wheel bearings in the "Girling" axle was revised downwards several times, I use the TR4 specification (which has the same bearings) of 5 strokes every 12,000 miles. Too much will force grease out past the dust seal and contaminate the brakes.
3) One of the dimensions for the rear main seal mandrel is wrong.
4) The wiring diagram is wrong for all but the earliest TR3.
5) I believe the starter "light running" current should be 45 amps, not 4.5
6) No mention of the later distributor, starter, generator, bolt-on ring gear, etc.
7) I don't recall offhand if the workshop manual proper talks about fuses at all, but the owner's manual in front of the Bentley reprint does. The horn fuse was later revised to 35 amps instead of the earlier 50 amps; and all of the fuse ratings are given in an obsolete British system that is roughly twice the rating of modern fuses. In other words, if you are going to use AGC fuses, use an AGC 20 in place of the "35 amp" Lucas fuse.
8) No mention of the fiber washer on the support post for the timing cover (which is also not in most gasket sets).
9) Conventional brake fluid needs to be changed every 2 or 3 years.
10) The recommended lubricants were changed in several cases. For example, starting around 1959 or so, they said to use GL4 in the gearbox & overdrive instead of motor oil.
11) Fuel tank capacity changed twice.
There is probably more, but that's all I can think of offhand. Oh, one more thing, when replacing the felt dust seal for the front wheel bearings, I think the procedure given in the TR4 workshop manual is much better. Basically you find the proper position for the nut before installing the felt or greasing the bearings, then mark the position and pull things back apart to pack the bearings and install the felt. That way there is no chance of getting a false reading from the felt (or grease) filling up the clearance. But you still have to be careful that the races are properly seated in the hub (if you replaced them).
Hey there Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
A friendly reminder - be careful what links you click on here. If a link is posted by someone you don't know, or the URL looks fishy, DON'T CLICK. Spammers sometimes post links that lead to sites that can infect your computer, so be mindful what you click.