I've run a D2/P38 with seeping HG's F/R for years a few times to be honest. #1 thing is keep the coolant level topped off, and always check it at every single startup. Backing the reservoir cap off a few turns would also help keep it from over pressurizing and causing the gaskets to gush. Now when I mean I drove like this I mean the HG's seeped upon startup, and once the engine warmed up the leaks stopped. If you reach operating temps and it's still leaking coolant = Do a HG job ASAP. If it stops leaking, and the coolant doesn't drop a ton then you can technically get away with it as long as the engine isn't stressed and causes it to overheat or over pressurize the system.

My 97 XD was seeping from all 4 corners when I bought it. I was in a rush to get it ready for it's first HCRR event so I didn't touch the HG's and like I said once warmed up it did not leak. I drove it like that for nearly 1.5 years without any issues. Then one day I was getting gas in the summer time and I noticed a puddle under the D1. I looked and it was green coolant. I immediately drove home and parked it. I found the leak at the back of bank 2 right at the coolant passage. I ordered a HG kit, and upon tearing it down I found a small line in the HG and a little line of rust on the head (poor XD was on a ranch in TX for 6 years without the proper 50/50 coolant mix) and that's where it was leaking from. Cleaned up the heads, and the block, slapped on the HG's and it's back in business.

So yes you can get away with it, but the one time you forget to check the coolant, or you stress out the engine = when it's going to fully go out on you. So it's best to attack it and get it over with IMHO.

 

Yes I know I have a HG swap in my near future. Thus far it is only very minor so I will watch carefully. I run the cap loose and check levels daily.