60->78 crossmember swap really tight

[60 Apache Shorty]

I need some help. I have a front crossmember out of 78 C10 all freshened up, new bushing/bearings, drop springs, drop spindles,, conversion rotors its painted and ready of install. The 1960 crossmember has been removed frame rails are in final stages of getting cleaned up so I thought I'd do a dry run. It looks like the 78 crossmember uprights are about 1/4 to 3/8 narrower than the uprights on the old crossmember. I've seen some great posts on here about reusing the top rear bolt hole I'm just not sure how I'm going to get it back that far. The frame gets wider as it goes back. At best loose fit I'm about 2.5 -3 forward of where I want to be. Looking for suggestions. Will things flex enough to get it to that spot?

At this point the front of the truck is resting on jack stands and I'm using a motorcycle/ATV jack to raise up the crossmember. I don't want to jam things too tight here as its just a dry fit before I paint.(was hoping to get holes predilled now) One thought was once everything is painted put the truck weight is on the crossmember fwd of its final resting spot then use as come along or something to pull it back, I'm just not sure I'll get it where It needs to go.