Bristol 100A engine

[Hydroglen]

I have a Bristol 100A engine and gearbox and the engine is 98% complete. I have some questions and or curiosities that some of you might help me understand.
1 When comparing it to my 85 in my Bristol 400 the most obvious external differences are the oil pan and the carbs. Triple SU vrs triple Solex. Correct?
2 The cam is different?
3 The crank is slightly bigger (2.130 diameter) than the specs I have for the 85.
Does anybody have the correct crank specs and what bearings are used. Alfa has been mentioned but year and model would help.
4 Rod journals seem to be the same as a 85
5 Pistons if stock weigh 240 grms..... Bob this may help you.The pin= 50 grms.
Pistons have a slight scallop on both sides near the pin area. Why?
6 Pistons have the number 5617 stamped on the dome. Also the diameter at 66.46 but this is Metric and = some 2.130"
7 The rod bolts are actually studs that have been pinned (see photo).
8 The rod bearing caps do not meet flush. The bearing surfaces meet, but not the outer part. Rather odd....see photo
9 Each rod is numbered but oddly. 371,376, 380, 384, 392, 400.What do the numbers mean? The rods weigh some 620 grms.
All help is appreciated, as I would like to work towards rebuilding this engine.
Other than a couple of scuffed pistons all seems to be in excellent shape.
Regards,
Dorien Berteletti