I guess I don't understand the issue. If the pushrods that came out are 10 5/8", the new ones need to be 10 5/8".

I've discovered that a lot of the sellers on ebay don't really know what they are selling. If a part is in a box marked 48 Corvette rod cap they'll list it as such even though it's impossible for that to be the case. If you don't know what you're looking at don't trust the seller to know any more than you do.