The Contract:

I Homer J. Simpson of sound mind and even sounder body blah blah blah yakety
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah 
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah 
yakety yak yak yak blah blah blah yakety yakety yak yak yak blah blah blah 
here by give Bart J. H. Simpson $0000001.00USD    ????????????????

Explanation:

The 16 '?' at the end of the contract constitute the 128bit hash of the previous step in the random walk.
The single '0' will be replaced with a '1' if the 8^th bit of the 128bit hash is set (the least significant bit of the most significant byte).
There is a 1/4 chance this will occur for any collision. The time to create one collision is approximately 2⁶⁴. The time to create one thousand collisions is marginally greater then that. So it is reasonable to expect if we can find a collision, we'll find one to satisfy our client Bart.

The contract is 3297 bytes in length. The final MD5 transform is:

state(32bit little endian) = 1e5bbbd2 4e8a2043 fc7a7aa2 f94895bd
block =
30 30 30 30 30 31 2e 30 30 55 53 44 20 20 20 20
?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??
0a 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 08 67 00 00 00 00 00 00

The 16 '??' bytes constitute the 128bit hash of the previous step in the random walk.
The single '0' is replaced with a '1' if the 8^th bit of the hash is set.

Now we do not require to compute the entire message hash, significantly reducing the computation required.
If the contract was in a word processing document, the 16 random bytes could be completly hidden from the signer in a hidden document property..