You may not need outriggers. I've seen a few smaller cranes like this one without them. Here's a photo I found online of a crane that's a similar size to yours: https://www.flickr.com/photos/desanno/4713963062 If you wanted to add them, you may have to change the wheelbase and move the trucks inward. Most cranes with outriggers have I-beams at the end that slide in slots. Slide one out on each side for outriggers. The larger 6-axle cranes usually have a set of outriggers in the middle between the trucks as well: https://www.flickr.com/photos/emd111/41017643180
Great info, and thanks a ton. At this point, I will either add I beams on the end sills on each side of the coupler or just do without. Since you brought up the topic of the crane's size and capacity...the hook with sheaves (sp?) may need to be changed to a simple hook with a ball and forego the double pulley system of raising and lowering the hook. That's probably overkill for a crane this size.
After looking at the photos you supplied, there may be a an outrigger--the pivot looking thing on the side. Maybe some sort of pivoting outrigger system could be built and incorporated. https://www.flickr.com/photos/desanno/4713963062
Good point, but at least that shows there are alternative outrigger designs. This one may be a bit difficult to scratchbuild though.
There are many ways to have outriggers and how to operate them through the years. It depends on who owns and operates the crane. The first I saw was steam power and at least three people in Oconto Falls, Wisconsin in the '50s when the paper mill was dominant. Then more in Milwaukee area.
Instead of starting a new thread, I just extended this one. The same neighbor has gifted me with yet more HO scale stuff. There are actually a couple of usable items in the box. After some online research last night, it turns out that the 30' flat car with the stake sides all the way around is a Roundhouse Oldtimer's 30' flatcar. It looks more like some sort of gondola to me, but that's what it's called. It's got Kadee couplers and metal wheels (now it has metal wheels). Tom Holley and I discussed it last night and he said it might make a unique plow. My assumption was a plow with a low blade either underneath or on one end. But every photo I've found has a large wedge blade on one end. Any ideas where an HO blade like this can be found? It may be beyond my abilities to scratch build it. I looked all over ebay last night. All that's there are blades that are part of a plow model. Doesn't make much sense to buy a plow model just to take the blade off and make another plow model. How would the wedge attach to the car? None of the photos show the attachment mechanism. Thanks!!!