To start welcome ,
When it comes to a turkey hunters gun , it plays more to everyones own gun and what they are looking for in the firearm. A single shot is a good idea due to the weight issue, and if you are planning too have the gun customized then there are a few things to think about.

First- "Gauge" 10,12,20
Second- "Shell size" 2"3/4,3",3"1/2 ( do you need the 3"1/2)and shot size- 4-5-6's
Third- Barrel Lenght
Forth-Chokes and the size
Fifth- Forcing Cone
Sixth- Sights
and so on ,
One thing to keep in mind ,no matter the size of the gauge of the gun and shell size, on a good average most guns will not kill cleanly out past a 45 yard shot.
Hunters are misinformed about a 3"1/2 in shell , they do not shoot any farther out then a good 3" load , they only have more shot in the load to give the shot a better pattern. We need to look at choke and constriction size and match a good turkey load to the gun.
If I was to start again with a turkey Gun I would also choose a single gun;
12ga,
22"-24"barrel with a lengthened forcingcone,
3" #5
Precision Choke .665,
Topped with a 1.75x5 Tasco scope
and a good sling and a good Quakerboy mouth Call <img src=icon_smile_wink.gif border=0 align=middle>...BT
I like them with Long Sharp Spurs....