Land and Sea Trailer Service

Here's what I've done to my 1972 yellow Land and Sea Trailer that came with 14.5 ST tires.

Go to 16" LT (light truck) tires - I use the same ones I  have on my E350 Ford (1 ton) van.

Tires
Dextero DHT2 Tire P245/75R16 109T

16" rims:
Rims

Taskmaster Steel 8-Spoke Trailer Wheel - 16" x 6" Rim - 6 on 5-1/2

The 16's won't fit under the fender so the additional clearance is accomplished using a taller equalizer:
Equalizer

Triangular Equalizer for 1-3/4" Double-Eye Springs - 6-1/16" Long - 9/16" Center Hole

I also replaced my springs

Springs

25 1/4 double eye

Wet Shackles

Shackles

Dexter Heavy Duty Suspension Upgrade Kit for Single Axle Trailers - Double Eye Springs

Tie plates that hold the springs against the axle (be sure to torque these)
Tie Plates 

Rockwell Tie Plate Kit for 2" Square Trailer Axle

Nev-R Adjust brakes (need left and right)
Backing plates

Self adjusting brakes are nice, but the hubs can be hard to remove to check bearings.

New upgraded hubs (and above brakes) for maximum braking
Hubs

6,000lb hubs vs the 5,200 that came on the trailer.

BTW - I removed all the bearings and races from the new hubs in favor of Timkin.
Off brand bearings

I get by fine with the electric brakes but I'm a very conservative driver. I'm thinking that EOH might be better for ultimate braking but I'm not willing to endure the complication.

Here's some more reading regarding the trailer if you're inclined.

Electric trailer brakes

Light Truck Tires

More on Hubs

More on trailers

New Coupler for Big Duck