Need help P38 4.6 with cooling issues

hi i wondered if any one can help i recently bought a rr 4.6 lpg its a preg lovely car and i allways wanted one i did loads of research a on problems and i eventually found one with low milage and that had recently had a new/re-con engine fitted all was good at first now its about 7 mnths later and started developing colling problems noticed leak in drivers footwell (thought o-rings )so i got new ones i need to fit but i noticed it was developing a miss fire so checked and found a couple of plugs were bad changed and seamed fine but then i noticed pressure in cooling system and thought head gaskett but as the engine is new ie block heads crank and all internals was very confussed as i am a mechanic i stripped it any waybut i havent really found what i expected it looks. ok oil in sump is milky and there was soom smoke from the exhaust before and it did have a slight miss i think it could have a problem with the block but am unsure as its only done about 3k-4k since i bought does anyone know how i could test the block at home in car still or have any advice as i dont wnt to put back together till i know is there a deffinat way of telling the block is cracked and last thing i dont know what company did the block but it has numbers on it any way of tracking who re-con it from these cos it should have warrenty but i didnt get any paperwork not really sure why guy just said he didnt have any need help i just want fix it thanks

welcome to lz, if your head gaskets where ok. i would be looking at sliped linner or your block has gone. get your self over to the rangie page..