extending a swinger

4130 chromoly 1" x 2" rectangular tubing. Best steel money can buy. It's a direct butt weld so you'll need to do some engineering to do it properly AND it's $15 a foot so you'd want to use it sparingly but here it is:

Wicks Aircraft Supply

I'd go with a foot of the .083" stuff and then tig it into the stock arm as close to the pivot tube as possible to minimize the shock it's going to see.

ORRRRRR you could just buy an extended swingarm and then sell your stock one.

you want to cut just after the shock mount evenly and use chromoly tubeing like SI said with a butt weld. As for your shock use the left over tubeing as your shock. To measure have a friend hold up the back end of the quad and measure a ruff guess of how long it needs to be to be stiff. this will hold up very well and will prevent wheelieing for the most part. Thats what my dad used on his shee and lasted 15 yrs no problem.just double check your measurements.