The 1.46 spring is supposed to be for hydraulic flat tappets and the 1.55 is supposed to be for hydraulic rollers.

You need at least the 1.55 in my opinion. I’m not sure thats enough, would be about 380 open, but its close. The springs for the solid rollers they sell are way too much.

The 1.46 springs would put you about 350 open.

Also, not to make you second guess yourself, but I just sold my new in box 240s and ordered the 270s a few months back for my stock stroke 440. The 270s are actually supposed to be delivered to me today. Engine Masters on motor trend tested the 240s vs the 270s and picked up 40-50 HP going to the 270s on a stock stroke motor with a small hydraulic roller (235ish @ .050 and around .550 lift). They didn’t lose any TQ, but only pulled it down to around 3500 RPM. They did run a super victor intake with the 270s and the trick flow intake with the 240s.

One issue with the 270s though is getting a good 4150 flanged MW intake.