the entire avionics package, to include Q-29 FLIR, SADL, MATT, radios, TACAN, INS/GPS/DOPPLER + CDU (Nav system), EFQI, remove ESSS and HF, install refueling probe and internal aux tanks (and their associated plumbing), defensive systems (EGMS, RWR, MWS), rescue hoist (we don't mount ours to the ESSS)...
Do your Limas have full-up 701Ds including the beefed up XMSN? Wide chord blades? Those are further differences that would have to be accounted for or de-modded. Even if these Limas were given to one unit so that only that unit had to deal with the differences ops- and mx-wise (assuming no de-mod), in the long run it would be hard, as all the units share aircraft to even out the UTE rates. We've borrowed A/C from the Guard/Reserve in the near-recent past at home and downrange and I don't see that ending anytime soon. Realistically what I see happening is a complete gut down to the 308 beam and then a rebuild as a carbon copy of a G.