Next week I'm getting my hands on a 4x4 np435, and transfer case, for a grand total of $200 as I am swapping to 4wd. (the front end is a future project.) My setup now is a 1985 f150 2wd with the 300 and the "4speed manual overdrive" or "srod" or "t170" or "doorstopper" or whatever you want to call it.

My only problem is I'm unsure of the crossmember I need and don't feel like swapping it in, to find I don't have the right one, then play musical transmissions until I find the right one. If somebody could describe what the correct crossmember looks like it would be a huge help. Pictures are of course even more helpful! Thanks

 

I haven't done the specific swap you are, but I've had four different transmissions in my truck over time........I haven't had to use a different cross member with any of them.

There are several sets of holes & slots in the middle of the cross member, for the rear mount; & the cross member is reversible in the frame. There are also two different positions drilled for it in the frame rails.

There was one swap (I don't remember which trans now) where I drilled two new holes in the cross member, for the rear mount bolts..........otherwise it has been just 'shift & shuffle'.

 

As Ken says, I think the crossmember is the same, though it may need minor repositioning. I know the trans mount is the same........
Ford may have used multiple bell housing patterns and engine mounting methods, but the trans mounting was pretty standard regardless of what trans (or engine) was used. Even when installing a newer trans that didn't even exist when these trucks were built, the crossmember generally works fine, but may need relocated a bit.....