I have never posted in the past. 1st I would like to thank all that give infomation. I have read these postings nightly and find them very helpful. I have a 1981 F-150 that doesn't have the orginal motor. I know its a 351M or a 400, was wondering if anyone could tell me what it is by the casting numbers?
They are: Block D4AE B2A 5L20
Valve Cover D6AE-9C485-ADB
Distributor D6AE 12127 DA 5K29
Harmonic Balancer 1 1/2 wide
The only other thing I have found was a yellow OK stamped on the head.
Rear End WDM-CJ 1D27 2 75 9 S314C
Transmission square pan 14 bolt is this a C4?
Any information would be appreciated!! This motor has been taken apart. Its obvious. :-X11

 

from what i understand (correct me if im wrong please), a 351m and 400 share the same block and heads, and the difference is the crank. i dropped my pan last night to get the number off the crank for a feller that wants to buy my engine. here is the website to find these bumbers.
good luck!

(block and crank
http://home.earthlink.net/~bubbaf250/parts/pics02.html

(heads
http://home.earthlink.net/~bubbaf250/parts/pics03.html