The 2.9 litre ford engine is actually a slightly longer stroke 2.8 litre German Ford V6 that has hydraulic lifters instead of solid. Although the original 2.8 engines were very popular in Europe they were only available here in the mid to late 70's Capri's. The engines themselves were very well made and could be counted on to turn 7500 rpm all day long as they had stout bottom ends. At one time you could buy 4 barrel intakes and hot solid lift cams for these engines but good luck finding this stuff today. Not that it matters anyway as the late model 2.8 and 2.9 have very poor head designs meant to perform emission wise. Of course you could find a 2.8 from an early Capri and drop it in but what would be the point, the best you could hope for from a 2.8 litre Ford engine is around 200 HP done to the nuts. Save your cash and do the 5.0 litre when you can.
BTW don't use the factory trans that came with your Bronco II they are made by Mitsubishi and can barely handle the 2.9 you have in there now, I know they make conversion kits for this kind of swap but trust me the trannies cannot take ANY punishment. The Borg Warner transfer cases are about as strong also. I would recommend you get the five speed with the motor and convert the truck to rear drive and forget about the 4 wheel drive. The rear axle is marginal as well as it is the 7.5 inch. I have assisted in this kind of swap twice now and both times the original driveline gave out after only mild abuse, I would even go so far as say that it would be wise to get a 9 inch shortened to fit under the truck. It would save you a bunch of trouble to engineer the truck right to begin with. They do go like snot after though because the trucks are so light. The second truck I helped with had a 400 HP 351W under the hood and that truck just about pulled the front wheels with a 4.11 rear axle....fun fun fun!!!!! Short wheel base stuff is a blast, you might want to put a roll cage in it to save your butt.
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”
— Han Solo