When you say lifter blocks I assume you're talking lifter covers?
I'm in the middle of reassy and I just installed mine yesterday. I believe the lifters will be in the way preventing you from sliding the cover out. You should be able to remove the top pushrod tube clip and slide the lower tube up allowing you to raise the lifter cover and clear the lifters. I've never done it but it seems like it would be doable.
S&S 4-3/8 stroker crank
Big Boyz Heads/CP Pistons - 10:1 CR
Andrews 37 cam
SE camplate/HO oil pump/tensioner upgrade
Dan Vance Ported TB (48mm)
SE II Slip-on's (soon to be 2-1 ST SuperMeg?)
Built by me with help from VTF