I'm in the middle of installing a 350 in place of my old Powerglide. Every post in this section concerning interchanging torque converters between 350's and 400's say they interchange. I'm trying to use a stock T400 converter in my rebuilt T350. It's hitting the trans case and it's flush against the flexplate. There's some cast-in round parts that are hitting the fins of the converter. It looks like I might be able to grind them for extra clearance, but before I do, I thought I'd check in here to see if that would be a good idea or not. It's a tight fit. A 12" convertor from a 70 Chevelle T400 should work in a T350, No?

There were some differences in bolt patterns, with the 153 and 168-tooth flexplates. Dimensionally though, they are the same in terms of fit with the bolt pattern exception with some, but not all.

Well, I went ahead and took the grinder to it. Didn't need much shaved off and it all looks good now. Maybe the 400 converters are a little larger?

Any idea what the original application of the TH350 was? I have actually run into TH350s with slightly smaller diameter bellhousing areas, one I used on a SB400 had to have clearancing done to fit the larger 14" flexplate. Another one I had in a v8 vega, and it fit fantastic..another v8 vega I did with a "normal" TH350 and it was a very tight fit at the firewall. Possibly the smaller bell ones were from 6 cyl cars originally?