I am currently working on this swap in my 73 duster. I had to widen the tunnel 2-3 inches and do some clearancing in multiple places as well as fabricate a custom mount.
I haven't decided for sure how to connect the speedo. I found a tailhousing machined for gears here http://www.transmissionsone.com/45rfe_performance_parts_from_pat.htm
pretty pricy though, so I haven't decided what route to go there.
I will most likely use a lokar shifter but am also considering making a custom cable shifter connected to my factory column linkage.