Adjustable pushrods for cam change
 

are adjustable pushrods neccessary when changing from stock cam to andrews 21?

No, you can use your stock push rods however, using adjustable push rods makes the job less expensive since they just cut your the stock rods and replace with adjustable push rods.

I think he's meant "less works", rather than "less expensive". :)

Absolutely not!
Are NOT REQUIRED.
As a matter of fact, you'd be wise to reuse your stock ones. Only means that you've got to pull the tank to pull them out.
Don't cause yourself any heartache, save yourself the money and reuse stock.

Your choices are;

Either buy adjustable pushrods
or
Rocker gaskets and disassemble as needed

Difference is about $100 in parts, and a couple hours of labor.

The choice is yours, but when I did my cam swap I chose to go through the top so I could change out the breathers to the new style and enlarge the rocker oil drain holes. And, I like the idea of having solid non-adjustable pushrods. I know the adjustables are very dependable, but the stock pushrods just give me peace of mind.

Not necessary but certainly less labor intensive.

I picked adjustables and i am glad i did as it made my top end a lot more quiet. A lot easier to me than going through the top...plus if you have to go in the cam chest again...VOILA....

I've never done a cam change before and I just installed the 255's on my SG using the SE tapered adjustable pushrods. The adjustable pushrods made the cam change a piece of cake. The engine seems really quiet now! You just have to adjust the SE pushrods 2.5 turns past snug. It is that easy.

The tolerances are not the best in the work in a pushrod system so the adjustables make the fit very custom. My motor was quiet for about 5000 miles then started to tick like a MOFO...How many times have you heard somebody say that they went to the dealer, bike under warranty , low miles and it makes a god awful ticking sound and they are told..."OH THAT'S PERFECTLY NORMAL"....BULLSHIT....the variance in the tolerances go the F^#$ to hell after you ride it for a while and it breaks in....I for one like a motor that doesn't tick....Now i can let it idle there and listen to it just sound smoothly, no ticks....
Then ride the shit out of it....