I’ve never used that site to make an Honda parts order, but the prices look good. Something I noticed when just looking at lower gear housings there. The part numbers & how they appeared in photos is different depending on models & parts store. I found a different Honda parts number for apparently the same gear box at Marine Honda.com, boats.net & Honda parts house. That seems strange as I now thought, the part number & diagrams for the gear unit would be the same on all the 40 & 50 hp models let alone different part numbers for the same model on three different web sites.
When I’m having difficulty finding the correct Honda outboard part & want to make sure, I’m getting the right part by finding the correct oem Honda part number for it. I first go to Honda Marine https://marine.honda.com/ They don’t sell directly, but I’ve found they have the best diagrams & accurate part numbers by giving them your motor serial number for the search or year & model number. After I’ve found the exact part & its number there, I normally go to boats.net to purchase. They have been very good to deal with though Honda parts house may be good too. The gear box is around a couple hundred dollar dollars more at boat.net than the Honda parts store.
I hope, I’m not making it more confusing as most likely all the lower unit gear boxes are the same for Honda 40 & 50, but as you said worth making sure before placing the order.
I overhaul and service dozens of outboards each year (its a hobby). Almost all parts are purchased from boats.net. It is the most reliable and timely service that I have found. Sometimes I purchase from local dealers, but it usually takes several weeks more time and cost but 20% more...