If you look under 1970 suffix codes at this site
http://no25.chuckthetruck.com/page3.html
TCK decodes as a 250 used in a Blazer/Jimmy application.

You could also put your block number in here
http://www.adchevy.com/tools/castinglookup/
for further confirmation.


"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson