OK Royce .... I see that link and all I can say is this .....

There have been links posted here that show a 454 being put into a 1974 Travco.

If you want to believe a 413 was available in 1977 ..... go for it.

The fact is .. is the 413 was dropped in mid-1973 because a 440 cost a TON less to produce. The PRIMARY reason for this cost diff were the 943 heads. ALSO .. the 413 block was special also ... that cost more too.