Re: balance shaft?
95's are a little confusing when it comes to the front timing cover. I am not sure when the sheet metal oil pan was changed over with the aluminum oil pan (like the 96 up have). I am going to asssume you just planning on using a used motor and bolting your intake on. If you looking to rebuild it, I would just find an older core (much easier)
http://www.syty.net/forums/showthread.php?t=20725
Basically if it has an aluminum oil pan I would drill and weld on a bung for the -10AN return oil line (also get a 90 degree fiting as well. If it has a stamped steel oil pan you can use the original. You can use the heads on the 95 block and they will bolt right up to you intake manifold. (they will probably be L35 with teh eyebrow on the intake ports) The 'W' Block has a more desirable cam, but the Z block has a simillairly anemic cam that our truck cam with. I personally I would change the headgaskets and head bolts with ARP's.
These motor have more Compression than our stock motors, so you will need to reduce the boost. 3-4 psi. You will most likely also need to do a custom tune on you especailly if it has L35 and W cam. I would not recommend a balance shaft motor unless the person is will to do a custom tune for their truck. If you want something that will bolt up and go, and not have to mess with tuning I would choose a different route.