Well I have just been through this exercise myself and fired my 54 up after 7 years and an engine rebuild just this weekend. The timing marks on the 100 are not extensive. There is a small hole drilled on the crankshaft pulley to indicate TDC and some timing chain covers have an arrow stamped on them. I am lucky my cover had a small tab welded on with a couple of marks. If you don't have a pin/tab/mark/arrow on your cover you can still get to the right place by first finding TDC.
I put some masking tape on a screwdriver put it carefully into No1 cylinder plug hole (the one nearest to the radiator) . By marking the depth of the screwdriver on the tape, removing it and rocking the car forward in gear and repeating, I was able to find the point where the piston was at its highest. Just be careful not to scratch your bores or piston. Once at TDC you can mark the timing chain cover at a point where it corresponds with the hole in the pulley. If you peer down from the front of the engine looking at the hole in the pulley and bring your line of sight to the left edge of the water pump body you can repeat the procedure and look at the same mark.
Your actual timing mark should be 6 to 10 degrees before this. As the pulley goes clockwise a second mark to the left of the first TDC mark (looking from the front of the car) should be approximately in the correct spot.
To get your distributor in about the correct spot you need TDC again but making sure you are on the compression stroke i.e piston up and valves closed. I simply did the screwdriver thing but with the rocker cover off checked that both the rockers on valves 1 and 2 rocked.
You can google the approximate orientation of the distributor to allow you to get the advance copper tube connected and not interfere with the coil. If you insert it so that the rotor arm when the distributor is fully engaged is pointing approximately at the number 1 cylinder contact on the cap (if your looking straight down at the distributor cap its about the 2 O'clock position) you will be close.
Firing order on the cap is 1,3,4,2 remembering rotor arm rotates anticlockwise.
Good luck hope the above ramble makes sense, I am sure the good and clever people on this forum will be able to simplify what you need to do and point out any mistakes in my explanation.
While i have run my engine, i have the carbs back in bits as I found it was running incredibly rich. I mean petrol puddle on the floor under the manifold drains rich. I bought new needles but never checked them and have now found I have BN7 needles in my H6's. I can tell you they are not a great match .
Dougal
Hi 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! >> 
