Peter,
If I may, I wish to share my exerience with head studs. I just had my '77 2.7 fully serviced at 190K miles. I don't know the full history of the engine as previous owner records are incomplete but, I believe this was the first time the cases were parted. Dilivar studs were observed on exhaust side and steel on intake side.
I was more concerened about the studs pulling than breaking and my engine builder's train of thought was that if they had not pulled by now that they will not pull in the future. So we desided to not desterb the studs at all (let sleeping dogs lie?). The engine was assembled and installed without removal of the existing studs.
Sure enough as I commenced engine break in and tuning, one of the dilivar stud broke, and so did my heart.
This time we replaced the dilivars with steel and installed time serts in the case. my engine builder was also beside himself for the bad advice and absorbed some of the costs.
I'm now back to tuning and have a problem with engine revs not dropping when shifting (see Cooler - CIS Trouble Shooting)

Ouch! I really don't like stories like yours, unfortunately they're all too common. The first mistake was made when re-assembly was attempted without doing the threaded inserts (I prefer case savers installed on a vertical mill, which insures that they are perpendicular to the case), this must be done on all virgin 2.7 liter engines. I must also mention that I would have put new dilavar lower studs in your engine, but that's too late now, just make sure that you re-torque the heads at your 1,000 mile service! Anyway, congrats on keeping a 2.7 liter running, and I'll catch up to your other thread later!