Bent struts

Mick,
I have only just read your post in relation to bent struts. Depending on how hard the strut has been hit,  the piston (shiny part) will bend where it protruded from the cylinder at the time of impact. This will restrict its travel.
OR  The strut housing will bend usually adjacent to the point of mounting. This is usually detectable by a keen eye.
If the vehicle is driveable, a wheel aligner will indicate a bent strut as either increased positive or negative camber if it has had side impact. If you have the struts out of it, use a metal straight edge in at least three positions to check along its length.
Yes the spring seat will get in the way.
The options available to you are to strip the original bits from the inside and fit a complete shock insert where available or to convert your struts to adjustable coil overs. If you choose this option, a regular subscriber to these pages has recently done it and I am sure will offer you the benefit of his experience all the way from the Camberwara district of NSW.  Good evening Pete.
Hope this helps  a little.
Regards, Al
 

A good indicator is at the base of the strut tube where it meets with the forging, if there is a bit of a bulge there then it's bent.