1977 904 horsepower limits?

In my world it will last as long as it will last in a 1900lb rail. in a car on the concrete in town on the highway I would be conservative with the abuse you give a 904 unless it’s purpose built like Plymouth 65 said no matter the age. Cousin has one behind a 340 in a half ton swb85 it has 85k original on it with a 318. When we put the 340 in his truck it lasted not long befor he had to get it built right. He spent about 1500 plus a converter to match the motor and it’s been his daily driver for about 10k. The new 340 makes about 400 on motor never sprayed in front of the stock 904