Best I can find is this for all
"WP" code Engines:
WP A-body 69 350 265 3-speed L-30 1x2 9790079 2 int seat 30
WP A-body 74 350 200 Manual L-76 K 1x4 488986 2 low comp
WP A-body 73 400 230 4-speed L-78 T 1x4 481988 2
WP A-body 71 350 250 4-speed L-30 1x2 481990 2
WP A-body 65 326 250 3-speed L-30 1x2 9778840 2
WP A-body 66 326 250 3-speed L-30 1x2 9778840 2
WP A-body 67 326 250 3-speed L-30 1x2 9786339 2
WP A-body 68 350 265 3-speed L-30 1x2 9790079 2
WP B-body 71 350 250 4-speed L-30 1x2 481990 2
WP F-body 73 400 230 3-speed L-78 T 1x4 481988 2
WP F-body 71 350 250 4-speed L-30 1x2 481990 2
Your code ( 516603) does not exist. Could be a factory warranty replacement block.
As you can see, the only FBody ( Firebird ) listed WP engines were in 71 and 73, The rest were basicly Lemans with 1 Full Size Pontiac B Body.
All WP blocks were for Standard Shift cars. Not Automatics.
Doug in P.R.
