Any bubble level around 2-3" diameter will work for level. The thing to have level is the turntable bearing. I usually level the crane with a 2'-4' level going two directions on the bearing, then mount a bubble level in the cab, using adjusting bolts to have the bubble match the bearing .
I'll take a picture of one tomorrow. Something like this will work. I would probably look for something a little more durable, but you get the idea.
http://www.ebay.com/itm/171557837991?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
My rt bubble is actually only 1" diameter, but I don't like it, its too small.
I just have some reflective tape and 3"vinyl number stickers, on the sides or bottom of a couple of the crane booms to indicate boom length. I'll mount it side or bottom, depending on what you can see from the cab.
Make sure when you mount your boom angle indicator, your crane is level, and the boom is level, when setting at zero. You can check it with a degree indicator.
Honestly, I would mount the boom angle indicator, and a bubble in the cab, but you don't have to put boom length on the boom (most cranes like yours aren't marked). If you need to know your capacity, it will be easier to get out and measure your radius, than to look at your boom length, then compare it to the range diagram chart. Then figure out from your angle, where your at for radius, and then come up with your radius capacity number.
It's easy to be off in the small range diagram picture, and if your really pushing chart, you'll want to be sure. You've got a lot of places in the chart where you're losing 4,000lbs of chart in a 2' change of radius. 2' isn't hard to be off using boom length, angle, and transposing to that small picture (from the seat).
If you pop out and stretch a tape measure, you won't be off 2'.
From 16' to 22' of radius, you go from almost 22,000lbs of chart, to less than 14,000. That's almost 1/2 your chart disappearing (in 6' of radius). And you can't see the difference between 18' of radius and 20' from the seat, but there's 3,100lbs difference in chart. Which is a big change relative to capacity, ie dropping from 19,000 to 15,800. Losing 3,000 lbs of chart isn't a big deal in a 140 ton crane if your going from 105,000lbs to 102,000lbs of chart, but you'd really notice it in yours unloading something off a semi.
Boom length is only really important when your capacity changes by boom length, which your crane doesn't, but if you want to put it on, go for it, more info never hurts.
On repetitive lifts, you will use your boom angle indicator, keeping your boom length the same. Ex. the truss pile is at 45deg. the first truss on the house is at 30 deg, and your coming up about 2 deg per truss as you come toward you across the house. That info makes it easier to come back to the same place on repetitive lifts.
If marking boom length. Boom length is measured from the center of the heel pins (bottom pivot pins) out. Not from the bottom of the boom.
. At least mine was out in BFE where no one could see me
