Maybe the 216? The 235 even has a relief valve. If you are getting 30psi and you have never seen it higher than that, it's because the excess bleeds off through a valve incorporated in the pump.
The reason for the full flow mod being feasible is the 235 uses the same oil pump and relief system as the 261 (full flow OR bypass) so we can be assured there is enough pump there to do the job.
So much so, they even mount the canister and original 1/2" lines up high on the engine. My contraption puts it lower on the block and uses 3/8" lines to keep things more balanced.
The 216 engine may be another story. It is not a candidate for a full flow modification. At least not with my current level of expertise.
