340 or 408?

So, I think you are asking it the 4:56 would hurt the longevity of the 408 more than the 340 you have been running. I have 60,000+ miles and 1000’s of passes on my 4” stroked 360. Went through it in 2016, bearings, rings, pistons(compression bump). Only needed a dingle ball hone. I spin mine to 6300-6400 to shift and 6800 at the stripe. 4:10 gear. In my opinion, there is ZERO difference in longevity between a 340 and a 4” stroked LA. I would go 408.