just pour some Fluid out of the converter into a pan or something you can inspect it..you will see if there is anything in there ..also check the pan of the 350 that exploded..if there is no metal shavings in the pan (dust i would not be that concerned with).
Yes The 350 and 400 inout shafts are the same. ( converter will work on both)
i would not buy an off the shelf converter...call and have you a custom one built for your set up...the cost will be about the same anyway.
Just reember a converter makes all the difference in how a car performs.
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "