I was getting ready to say no Holley unless that engine and head have had some extensive work done. then I went looking for a link with info about the flow capabilities of carbs, thinking to suggest the Weber 32/36 DGEV or the 38/38 DGES -- turns out the DGES can flow 390CFM, as well, though I'm not sure how many folks run those on the 20R engine; many in operation on the 22R though.http://www.off-road.com/trucks4x4/article/articleDetail.jsp?id=274605
it's my understanding that high flow carbs still work, but I think the idea is that they take some engine speed to wake up, and that the smaller carbs tend to offer better low to mid range throttle response due to the velocity of the mix.
after some quick reading on that Holley carb, it seems that it's a progressive carb with vacuum secondaries? that's a good thing. progressive carbs make for good driveability, but may not flow as much as synchronous models. most people tend to think bigger is better, but not with induction if your engine's not built to move the air and fuel.
is this the Dual Plane Offy intake? if so, the intake and carb are probably a pretty good combination! I say leave it on, and learn as much as you can about getting it tuned properly. post up some info and photos and let's see if we can get it dialed in for you!