I've had my lifters in and out with the heads on, but I'm running magnum heads so I'm not sure if it'd be too much different.
One of the blocks I looked at was a 340 spintron block that had solid rollers in it already from the last time they were running small block Mopar tests (probably back when dinosaurs were still roaming around). I don't recall what lifters they were exactly, but I had to pull the heads to get them all out. If I had thought about it I would've checked with the hydraulics and thrown my magnum heads on to see if there was any difference in clearances but I didn't think to check.
