BBC Transmission Tunnel - High or Low!?!

[LOW 7FO]

Hello All. 1975 factory big block truck here. Also has TH400 although I cannot prove it is the original trans. From everything I read it says that I should have the high trans tunnel...but I don't! I have the low tunnel and the carpet kit I bought for the 1975-1980 with TH400 does not fit the tunnel area worth a darn (way too loose).

So...is it possible that this truck came with a TH350 and received the low hump? Other thoughts? I know the VIN is accurate and the truck is a factory big block so I am kind of lost now as to what the heck is going on.

I am now going to just order the 80/20 loop carpet for the 73-74 trucks since I like that better than cut pile and now I know it will fit my trans tunnel...