I just bought a GT shortblock with the intentions of using it with my 4V heads. I made numerous phone calls and read lots of posts that said the blocks are the same with the exception of mabye some timing cover bolts. WELL... I just got the GT shortblock today and found another slight difference that may prove difficult to deal with. When looking on the front of the block, there are 4 dowel pins on the GT block that are driven in. They are for the timing chain guides. On the cobra block these are threaded and the dowel pins are a different size. Sounds like no big deal but the dowel pins I must use (COBRA) are threaded with a much smaller thread than the hole the pressed in dowel pin leaves. If anyone has any tips, let me know. I guess I can tap it and have about 2 or three helicoils in those holes but I would rather avoid it if anyone has any ideas or has ran into this.