engine help needed!!!

I am in need of help on figuring out my motor. Maybe someone here can help me??

Block # is:
3951509 400cid, 2 bolt main?

Engine ID/VIN #'s are:
F0815TLT looks like Flint, MI, Aug. 15 possible 1975?
G97101950 haven't figured out the bottom one.

Still need to find Date stamp?
Can anyone PLEASE HELP ME???????
thanks

Upgrade to my last post.....

Found the Date Stamp #'s for my block. So i think i have it figured out.....
here are all the number's.....

Block Stamp:
351509

Block VIN/ID:
F0815TLT
G97101950

Date Stamp:
H128

Looks like i have a:
1968 Chevy Sportvan 108 with a...
1978 Chevy Light Truck Block,
400cid with a 2 bolt main and a
2spd Automatic Power-Glide Transmission
and as you might very well know she hauls A**!!!
with new brake system, all bugs fixed now Thanks for your help!

All-Righty-Then..... Sounds like you figured it all out on your own. Congrats on the van...