[Biturbos4] Interstate Battery replacement

[Aaron]

I bought an Interstate replacement battery for my 01 $4... interstate's website clearly indicates that I need an "MTP-91"... which when bought, does NOT match the size of the stock battery.... it will fit depth wise, but not lengthwise.  Anyone with any experience in this matter?  I'm a big fan of those batteries, so I'd like to stay with them.  Thanks.
Aaron LaPointe
01 $4