Getting the most power out of my 400 stage 6 heads

Ah ok I got you now, I was just thinking I'd have to order a set of pushrods and all for a cam I'm planning on throwing away, which honestly I don't even know where the 509 is at the moment, I've been In the process of moving since me and my ex split up it may still be in the shed at my old house.. But if I do get it I guess I could use the pushrod length checker as a pushrod to check valve clearances I didn't really think about changing heads would effect it tHat much but I guess with a little bigger valve it could make a difference, and also being I'm putting my Harland sharp true 1.5 rockers on vs the stock rockers which they say aren't a true 1.5 but actually less can also effect it which I forgot to mention the 906s I pulled off it had the crap shaved out of them, comparing them to an uncut pair of heads that came off my 440, they were dang near shaved down to being a closed chamber lol, not much of the meat left on the open part. I don't remember now exactly what I'd cc'd them at but I want to say the 906s were cut down to an 80-82cc. an above comment said that my stage 6 heads have probably had a lot of milling done to them, I don't think they have, from the specs I've looked at of stage 6 heads for sale online in stock form, they have a 75 or 78cc chamber, so would it really take that much milling on such a tight quench chamber to cut off 8-10cc? I'm sorry I have so many questions I've never had this situation, I've never thought about putting a big cam in a no valve-relief engine before, also I've not messed with many big blocks, I grew up with small blocks and this will be my first engine I've dealt with that had adjustable shaft rockers, we either had stock shaft rockers, or magnum style or stud mount rockers. There are some things I know more about with engines but valve train geometry is one area I'm a little less educated on. Doesn't Valve lash reduce or increase lift and duration? Also isn't the intake valve at full lift when the piston is on the down stroke and at bdc? And isn't the exhaust valve full lift on the up stroke and at Tdc? Also wouldn't a wider lsa be more forgiving on valve relief than a smaller lsa? Like say for example wouldnt a 114 lsa 509 be less likely to hit a piston than a 108? I've done some google searching on the subject and one guy was saying he had a 400 with the .528 purple cam with 1.6 rockers, but the .528 also has a 112lsa and smaller duration, doesn't it? I guess the main question should've been what's the biggest cam that someone has used on stock type Pistons, but I know what may clear in one engine may not in another, I'm just trying to get an idea of what I need to look at, I know with theSe heads I'm handicapping the potentionial with a small lift and small cubes which I'm saving up to get a stroker kit, but that'll be a ways off, but for now I'm trying to get my car running for an event in October and also want to get back on the race track... I've been off the track for about 8 years now... But being I don't have the ex ole lady now which the night we met I was in the process of putting a 500ci stroker into my roadrunner, but when I got involve with her, we ended up having a daughter, and I sold my stroker and ended up putting cars on hold, I'm regretting selling that 500 now because I'd be putting these heads to good use on it now, it had iron heads 2.20/1.81 valves, full port 906s on it, anyway, I think with the 400, i think these heads will flow plenty well enough with a .500ish lift to feed it, and I think it will probably want to pull past a safe redline, which there's guys out there says oh I've revved stock 383s and 400s to 8 grand before, but I don't want to do that, I want it to live and see that stroker crank in the future... What's a safe rev limit for the bottom end on this motor?