While we do not have a custom fit trailer hitch receiver for your 1989 Grumman Olson, we do still have another alternative.
Instead, you'll need to use either the:
-7" Weld-On Bracket Kit for Draw-Tite Class V Ultra Frame Service Body Trailer Hitch # 4907, which has a 7" drop.
Or
-The 16" Weld-On Bracket Kit for Draw-Tite Class V Ultra Frame Service Body Trailer Hitch # 4916, which has a 16" drop.
From here you can use the Draw-Tite Ultra Frame Service Body Trailer Hitch # 41990-16.
This... view full answer...
The LED Trailer Tail Light w/ Reflector # DG52721PB that you referenced is sold as an individual assembly. If you needed two of these you'd want to order a quantity of 2. view full answer...