I got the retrats from SouthEast models. They are supposed to handle 5 to 7 pound bird.
Though I'm starting to see a lot of wear in the nose gear where the strut goes into it.
I have a heavier nose unit on the way. Could be the rough strip is just too much for the standard system. I use the local soccer field and the so/so conditions are pounding the nose gear. Not a cheap set up. Kit was around #300.00[X(]
As for wheels, all I did was replace the stock foam ones with the closest size rubber versions.
The foam ones flat spot badly and I also found the axle holes weren't even close to being in the center. On driveway taxis it looked like a drunken sailor, wobbling back and forth.

I didn't take any shots of the install. Though I can pass on some tips.
Build the nose unit on a piece of 1/8" lite ply outside the bird. Makes setting it up so much easier. I then went in and built up the formers to support the lite ply. Then just slid the whole shooting match in through the back of the center pod and into place in the front.
Where the gear exits the fuselage instead of trying to trim everything, I cut out a big section of the balsa sheeting then made up cardboard templates to get a nice fit. Used the template to cut out a new balsa sheeting, and used a pair of R/E magnets to hold the piece in place. Covered the new hatch and painted it to match. Makes it easy to access everything by just popping off the hatch.
On the rears I left them open, went the PITA trimming method. That way air can get out to aid in cooling the motors and esc's.
What else???????? Oh, I moved the nose wheel back to a more realistic position, and had to play with the retract angle and strut to get a slightly forward rake on it. Ended up having to cut out some of the lower formers and boxing them in to get the nose gear up in, in the retract position. On the rears same thing, though the wheels won't go up in fully. About 1/2 of the wheel sticks out when retracted. Just not enough room where the booms are cut out for the wing to get a full unseen wheel.
I mounted the tank,servo, and valve in the center pod at the back. Used lots of line and quick connectors so I can dissasemble the booms and center pod if need be. Rx sits under the wing in the center pod, right at the LE.
If you need any help give me a holler.