water leak at headers

I have come to the fountain of all BB knowledge I hope. I have a 440 complete rebuild . I removed the stock exhaust manifolds and put on long tube headers. The bolts going into the heads are not sealing and drip quite a bit . One of Mopars better ideas was to have the bolts enter into the block water jackets. I am having no luck sealing the rear bolts . The original manifolds had studs threaded into the jackets and they could be sealed but I can't put in a stud and still get the headers on properly. Any suggestions for this other than going back to original stuff , would be much appreciated.