Is this just a semi auto M-14? If not what are the diffrences....barrel length?

different manufacturer, springfield armory incorporated(who makes the m1a) is not the springfield armory that made the M14 for the .gov(though they'd like you to think they are, hence the name).  they are basically the same, without the hole for a full auto selector that the M14 had, and with cast receivers and parts rather than forged like the USGI m14 has.

The older SAs can be had with all GI parts but for the reciever. They are the one's you want to look for if possible but you either have to look at the parts to check numbers or get lucky like I did. Mine was an all GI gun, BBL included and I quite frankly lucked out on finding an 80s M1A that was basically unused from day one. As I got a case of ammo with it and around 50 were gone I am assuming from the condition and lack of wear that that was about all that went down the pipe.

Look for an older SA with CL GI BBL, bolt, trigger group, sights, gas assy, flash hider assy. If you find one at a good price it will be a good gun and hold it's price well.

Actually, not all older M1As have GI parts. Many people assume this but its not true. SA has had many rises and dips as far as being able to get USGI parts. Most of the real early ones are all USGI but in the early 80s they ran slap out of GI parts. I had one made in 1981 that did not have a single USGI part on it. I had one made in the late 80s that was virtually all USGI parts. The reason for this is a large amount of Isreali used USGI parts were reimported into the US in the 80s, reinvigorating the M14 parts market. As of the last few years theyve run out again and many of the newer M1As Ive examined have had very few GI parts. The parts you really want to be USGI are the bolt and operating rod for sure.