hey guys i may be getting an all original very nice 521. i dont want to cut of the truck what so ever as  it has just been repainted. can i wedge an l16 or l18 in it with a 5 speed without having to cut the firewall and such. i am pretty sure the late 521's maybe 70-72 came with an l16 but i am not sure.

I don't see why that wouldn't work.  They're basically the same truck except for the drive train.  You have an L521 which came out for the 68-69 model year with the J13.  The PL521 actually overlapped the 69 model year and ran through 72 utilizing the L16.  You'd probably need that five speed since your stock rear end is 4.875 and the PL521 had a 4.375.  The 'dog leg' five speed from a 77-79 200SX or 78-79 A10 (late 510) would probably be the closest to a bolt in.  Hopefully, the pictures are clear enough.
[img]http://i22.tinypic.com/ruy59g.jpg[/img][img]http://i23.tinypic.com/nef9ll.jpg[/img]

thanks so much.