Short Vs. Long Gear
I'll second what George said. I considered this change on my short geared RV-4 also, but ultimately decided not to do it because of the large number of other things that have to be redone when making the conversion. My O-360 powered -4 started life with a 72" Sensenich. Off hand, sitting here at home I don't recall what the static ground clearance was but the measurement from ground to spinner tip was the same as another -4 we had in the hanger at the time. So, I think my plane is representative of the breed. As part of my worrying about this issue, I did tip the airplane up until the prop was just tangent to the ground. The nose down attitude in this test was very low...and would certainly get your attention if you tried to wheel-on in this attitude. (Granted it didn't include pilot weight, landing dynamics...blah..blah...blah...)
Here is a picture where I had the plane in a static attitude with the 72" Sensenich, and it looks like about 5 inches of ground clearance, but I can't tell from the old grainy photo.
[img=http://img527.imageshack.us/img527/3850/image1082iw.th.jpg]
Having said all that, I did switch to a 68" diameter Whirlwind 151 constant speed prop about 150 hours ago. There were many factors in that decision, and without getting into any of the debates that switching to that brand and type of prop could spawn, I will say that improving my ground clearance was a factor.
Another thing to consider is the over the nose visibility. With the short gear, I have excellent straight-ahead visibility...this would be degraded somewhat with the longer gear.
The short vs. long gear thing is certainly a personal decision, but as George pointed out, it's going to be a lot of time and money to switch to a long gear, and for me...not worth it. Most of the time I try to land in a 3-point attitude or very tail low so the short gear is not a factor.
Though I hate to recall it, perhaps this story will make you feel better. When I first completed the -4, I proudly flew my new plane to Stephenville for lunch with some of the BCs. I elected to do a wheel landing (with the 72" Sensenich), but botched it badly by misjudging how high I was and flying into the ground way too hard. The initial contact and subsequent bounces were high and hard, but the prop never contacted the ground. Now, let us never speak of that event again
Good luck!