[iluv69s]

Yenko started making the blocks after 69 and they apparently made various versions. Some being tall deck for larger stroke/ cubic inch options. There are some past threads on the subject here if you do a search. The SYHE is commonly stamped in the timing chain area. I have many fotos of different types/configurations on the ZL-1/Yenko alum. blocks. Some had push-in freeze plugs and some screw-in. Some had Winters foundry logo..others had different founndry..there were various different YENKO letters and/or insignias. If you PM me, I can see if any seem to match your block.