Ahhh, GOOD MAN!
You pay attention, you ain't a-feared, and you're asking pertinent questions, that makes helping you easy.
A>Swivel plates=2-12"x12" vinyl/linoleum floor tiles from Blowes/Home Cheapo $.60-$.95 apiece for each side with fresh wheel bearing grease between the shiny sides. MAKE SURE CAR IS ON A LEVEL SURFACE< SIDE TO SIDE AND FRONT TO REAR!!!!!
B>If you buy from Speedway (or other brands/models), note that different brands/models have different number of maximum degrees that they can measure.
C>It's actually 20 degrees one way and 20 degrees the other way (at least for the Longacre unit I linked).
For example:
On driver side you turn the wheels to the left 20 degrees and "zero" out the caster bubble then turn the wheels 20 degrees to the right to take your reading. Do the opposite on passenger side. Note that at the outside end of the gauge, there are 2-20 degree angles formed into the body of the gauge. you can line them up pretty well by leaning over your fender/hood and use the straight edge of your fender to get pretty damn close. Following repeated tests, I've determined that this wil get get you to within a 1/16 of a degree or so, depending on how anal you are about dividing the bubble readings, which are graduated in 1/4 degree increments, ya just gotta do a little fractional math.
Once you monkey with this a couple/few times (to try different settings to your preference), you will NEVER **** away another penny to have some half-a$$ed alignment shop get you within "MAYBE" 1/4- 1/2 degree of what you really want.
You can purchase a box of shims at harbor freight:
http://www.harborfreight.com/144-piece-body-shim-assortment-67585.html
Some tips for you to minimize shim differential between front and rear bolts of the upper arm and have the best driveability/tire wear:
A>CASTER-Remember that extra "positive"caster will make your wheels a little tougher to turn, but add a bit of stability. When you get your new
upper control arms, carefully hammer/press the mounting bolts out of the shaft and turn the shaft (which is threaded) one full turn to move the arm to the rearward of the car (for the side you are working on) and then put the bolts back in. Before doing this, take measurements, as not all upper arm shafts are actually centered to the arm.
This will provide a little positive caster before shimming. If you find you need more go another turn. You "COULD" go 1/2 turn at a time, but many after market shafts have a groove cut into the threads for grease distribution, although I'm not positive about if it really matters about the groove being at the top or the bottom. I would go for 3-3 1/2 degrees positive caster, minimum 2 1/2. Bear in mind that some "Shelby drop templates" are already set up to move the arms 1/8" to the rear, to give some positive caster, as opposed to simply dropping straight down 1".
B>CAMBER- Set your camber after setting the caster. As long as you add the same amount of shimming to the front and rear bolts, the caster should remain generally the same, but recheck after you achieve desired camber. I like to keep the camber in the center of the zero-negative 1/2 degree range at 1/4 degree or a tad less for nice tire wear.
C>TOE IN-About 1/8 inch toe in is a good start. Use a tape measure across the rear of your front tires at an easy to duplicate part of the tread and low enough that the tape measure meets no obstructions. do the same at the front of the tires, on the same part of the tread pattern and shoot for the front measurement to be 1/8" less than the rear. Please note that the wider the tire and the more negative offset (tires/wheels sticking out farther/deeper dish wheels) require a little bit extra toe in to, say, 3/16" or a bit more for good, positive "return to straight/center" response. The little extra toe can lose a couple miles of tread life, but I personally don't mind the small sacrifice for added stability.
Also, bear in mind that the closer each side of the car is to the other, the more stable the steering will be!
One last item, that probably should have been the first, is mounting of the gauge. Before you purchase, please, if you can, post a pic of one of your wheels and center caps/mounting hardware with the wheels and caps removed from the car. If the wheels are aluminum , the magnetic adapter won't "adhere" to your wheel without a little imagination and if we can see them, we can help you make a plan. For example, you could buy the gauge without the adapter and buy a separate adapter that fits through the hole in your wheel, onto the hub with the grease cap removed. On the other hand, I have Cragar SS wheels with a center cap that has a steel washer inside the wheel for mounting an I simply got an extra pair of caps/mounting washers and used an extra washer with a #10 bolt/nut mounted to the otside of the wheel for the standard magnetic adapter. Ahhh, Rube Goldberg was my hero!
HTH,
Gene[/quote
I purchased two caster / camber gauges used on eBay. I will sell the one I don't like as much. I plan to reinstall my engine early November, so questions to come...
How did the alignment go?
Fit perfect with a little space to spare on my 68. 
