Help destroyed 7 1/4 in a /6 dart

I ran one behind a 340,
in a 65 Valiant wagon,
for two or maybe more summers I think it was.
When I blew the 904, I gave it to my little brother, who swapped out the 340/904 for me, and put a 225/904, that I supplied, into it, and then he drove it some more. I still have that 340/904, some 45 years later.
Hang on, confession time;
That 340 had a 318 top end on it and a 318 cam in it. So it was really just a big-bore 318, but man it was wicked.