Ok here it goes. I am swapping a 5.7 hemi into a 66 coronet that has the original 727 small block. I read the thread on swapping the hemi into the"ole mopar" here on moparts. I have the exact SFI flex plate called out in the article right down to the part number (P5153753). Today I held up the flex plate to my torque converter and it is about an inch off in the bolt patterns. The SFI plate is about and 1" too small for my converter. I don't know much about torque converters. Can someone clue me in? Do I need to get a smaller converter? What size did the 66 coronet come with? I read that there might be an issue with the 66 model 727 having a different number of splines than the 67 and newer. help I am drowning over here! I am ready to drop that 5.7 hemi ins and can't!

Bump

I held the new flex plate up to the old flex plate and the old torque converter. It really wasn't even a close fit. My flex plate does have two holes drilled in it at each ear but they appear to be set at the same diameter. I held the new flex plate up to the hemi flex plate that came on my donor motor and the bolt holes match perfect, but when I hold it up to my old flex plate they just don't match.

FYI to anyone who finds this thread, I ended up having to buy a custom torque converter from TCI to make this work. The flex plate I goty from mancini was not suitable for my application. I have found several threads on line with people telling you how to make this swap and none of them seam to have this problem. I have 4 torque converters sitting in my garage. One from a 65 cable shift BB 727 and two from SB 727s (one 19 spline and one 23 spline). They are all identical as far as torque convertor bolt dimensions. None of them would have worked with the Mancini plate. When I bought my custom convertor from TCI it was dimensioned the same as the others as well. I had to send it back to TCI and have them move the lugs on the TQ to suit the flex plate.
On a related note, make sure you have the lugs of the TQ 7/16" holes. If you go with 5/16" it will not work with the flexplate unless you by the shim kit that Mancini sells for $30 + shipping. The added thickness of the shims means that you lose thread contact when you do bolt the flex plate to the TQ. This could easily cause stripped threads. I had it happen twice. I eventually took the TQ to a machine shop and had it drilled and tapped to 7/16". I could have saved $40 on the shims and $40 on machine work if I had only have the 7/16" lugs from the start.

Your last post makes no sense, Mopar has used two different diameter bolt circles on 727 converters, 10" and 11". The original '66 would have used the 11" bolt circle, if you got a flexplate with the 10" bolt circle it obviously wouldn't work, all you needed to do was get a flexplate for the 11" bolt circle. Sending the converter back to have the drive lugs moved was an unneccessary expense, TCI should have advised you to that.

A change in the thread size of the drive lugs shouldn't necessitate a "shim kit", sounds like TCI screwed you all around.