i need help

ok heres the story. i have a 98 cobra that i have swaped the motor in for a case iron block with 03 heads and 99 intake. my problem is that the shop that is trying to get it tuned for me is telling me that the belt is comming off and that they cant find the problem. they are suggesting that i replace the timing cover with the factory one off my original motor. now my problem with this theory is that the timing cover is not a mounting point for any ribed pullies. so i guess my question is this. does anyone know of any variations between the different block castings, do any of them mount the alterenator in or out any further than the other and or are either the powersteering pump or the ac mounted any further in or out on the other blocks iron vs aluminum this is a 4.6 to 4.6 swap so were not taking 5.4's here. any help you guys could offer would be greatly appericated. thanks

Aaron

i havent had a chance to look as my info is comming from the shop that soppose to be hammering out out the little stuff for tuning. how ever when i did install the belt origianly the water pump did not seem to be any different than the one on my origanal engine. plus the water pump pully is not ribed so i dont thing that it would cause the belt to jump off instantly as the shop is claims that it does.