depending on what year may determine how hard it is, but I think you can put just about anything on anything if you try hard enough....search for a thread titled '100% bolt on saginaw'
I have a 1990 351, trick there and for the 302 is to get the bracket from the same year range ford van and use the pump and pressure hose for the e series van. on the 351/302 the power steering pump and ac compressor share this bracket. the brackets look the same, but the bracket on the van has the mounting holes for the saginaw pump versus the ford pump. the ac compressor bolts on the same, but I had to get the bolts for it that went with the van bracket as they were smaller diameter than what was on the original bronco bracket....leave it to ford to change that little detail. I think you can see the saginaw and the bracket in my photobucket. not sure on your 4.9, but it may be off on its own bracket or may share the bracket with the alternator instead of the ac compressor-but still-the van bracket should be the easiest way to go and basically a bolt on