Here's a view from the top. The Mag bracket will ALMOST bolt up to an old-style LA manifold, but there is an AC boss (lower right on manifold) that gets in the way. If you use the Mag AC, just hack the boss off, if you're in love with that manifold. If you're not using AC, just hack the boss off, and...

Also, the LA t-stat will PROBABLY work, but you'll PROBABLY have to hack part of the AC portion of the bracket off on the Mag bracket. This is the part on the upper right part of the Mag bracket, and the AC part is framed by the four square bolt holes that you can see. Note that in the pic, the intake manifold is moved back towards the rear of the engine by about 1.5" so these two issuse will clear. There are also some small brackets that stabilize the ALT and AC on the intake. You'll have to sort that out if using a non-M1 EFI type of manifold.

Clair