Hi Spyke,
Regarding the cracks around the bronze inserts
I have been told that some of these have been there since casting, the alloy shrinks faster than the bronze and the cracks occur!!!!
Screw a rockerbox bolt into the threads all the way and try and see if there is any movement of the insert
If there is no movement I think I would be happy enough,also check if the bronze is proud of the face
I dont knonw how the alloy welding would work if you ground the alloy back to the bronze ????
It is vitally important to clean out all the crap that accumulates at the bottom of the insert holes
I use a 1/4 drillbit first and then run the tap down then drillbit again followed by a blast from the airline
I have sent a badly cracked head to SRM for estimate, one insert is broken out completely and another is very ropey looking, a 3rd insert has damaged threads!!!!
In the meantime I have bought another head on fleabay from the USA, this turned out to be quite a find as it is complete with no damage at all!! and included the rocker box and all the fittings
There even isn't any distortion of the ally around the plugholes or headbolts,
I dont believe the engine had any real miles up and was never apart before
Regards
John O R