Get the guides from pontoonstuff.com
https://www.pontoonstuff.com/products/pontoon-trailer-guide-ons
I bought these and have been very impressed with them. I had looked at others, but the reviews were all over the place. Most of them bend or don't work very well, and I didn't want to take my trailer to a shop and have them fabricate custom guides.
These are very strong, and have a nice glossy powder coated black finish on them that looks like it will stand up well to the water. The 2x4s can be removed and recarpeted easily if need be at a later time. They bold right onto the cross beams of the trailer with 4 bolts (2 U-bolts) on each guide.
Pontoonstuff.com was great to do business with. Fast order confirmation, fast shipping, and great communication. Buy with confidence.
club.benningtonmarine.com
She even bought both of us t-shirts that say "sorry for what I said while docking boat" Kinda funny seeing someone in Covid-19 face mask yelling obscenities while trying to hang onto docking ropes. 
Haven't been out to try them yet. I will paint exposed brackets with a rust proof black paint eventually. Note that both brands of guides have 14 gauge metal and an angled brace welded in for strength. Not all brands are as reinforced. Almost the same initial cost but some are made huskier. Didn't opt for galvanized as we only go to fresh water rivers and lakes.
