I found the depth of the torque converter offset to be different between the C6 and the E4OD, but the bolt circle matched perfectly. The offset on the E4OD was ~1", the C6 was closer to 1.25. This is just what I measured myself, I don't know what the official specs call for.
Regarding the adaptor plate. I'm trying to find some images that show what I am talking about, but this isn't a part that normally gets googled. I'll try and describe...
The older IDI diesels have bell housing bolt pattern that consists of 6 bolts (same as later in that respect). The 4 lower bolts go directly through the adaptor plate and thread into the engine block.
The upper 2 bolts on the engine block are used only to hold the plate against the engine block.
The upper 2 bolts for the transmission bell housing thread into the adaptor plate ABOVE the upper 2 engine bolt locations. In other words, the older IDI style adaptor plate allows for a larger bell housing for some reason. I have no idea what this reason is because this offset is eliminated on later powerstrokes and thats what I'm trying to warn about.
On later powerstrokes, the upper 2 bolt locations on the engine block and bell housing are one and the same, so the later powerstroke adaptor plates are not as tall, and those era of E4OD bell housings are sized to match the new style. From what I understand, the 2 different styles of adaptor plates and bell housings will not interchange, however if they are kept together (same era tranny with same era plate), they can be used on older IDIs.
I personally saw this on a 1995 powerstroke with 5 speed. The adaptor plate was only spacing off the transmission by it's own thickness, it did not change the bolt pattern of the engine block and all the bolts went clean through the plate while only threading directly into the block. I don't know the exact year of the change over, but it seems that it happened after the powerstroke engine was introduced. I can't be sure, but it might have something to do with the 7.5L being phased out. Bottom line is there are 2 different adaptor plates among the IDIs and early powerstrokes.
I hope that makes sense and I'll see if I can locate some images of the different adaptor plate designes used on the IDIs verses the later powerstrokes.
If you got the transmission to bolt up, then you have nothing to worry about unless the torque converter is stiff against the flex plate like it originally was in my case.
