I have recently acquired a rifle with what I'm sure is A MVA #107 tang sight. 
1) the rifle is a 30-30 lever - 
  A) is that "too much" sight for 30-30?
  B) would changing to a "mid-range" be more realistic, given the cartridge and action?

2) I have a Danish roller in 8x58R would this be capable of using the long-range sight?

At 700 yards, a 30-06 cartridge will typically have a velocity ranging from around 1100 to 1450 fps, the drop will be around 130 inches.
At 500 yards a .30-30 rifle will generally have a velocity around below 1,000  fps and drop 126.5 inches.

I have a MVA 133 mid range, their basic tang,  on a 24 inch barrel Marlin 336 30/30. It’s good for cast bullet modest velocity loads at 200 yards. Use it in occasionally club Cowboy Lever Silhouette. It’s not competitive due Ram Knock down % but very accurate and easy to shoot.

Bought the rifle on line intending to convert to 38/55 arriving found it’s too nice to alter, I did D&T the tang . Gun is about 1952 vintage some 36’s and early 336 guns were D&T for tang sights.

Couple points, cast bullet typical velocity 38’s & up 1200 fps plain base . Gas checked 30, about 1600. Slower the bullet more sight elevation is needed.

My gun the mid range is ideal and will also zero 300 yards. However if I had a long range MVA on it would probably sell off the sight and replace with a mid range MVA. Any MVA easy to sell and the Mid range is more appropriate. I see Marlinguy has the same opinion, he’s the Marlin expert here.

Boats

32” gong can be hit pretty consistently at 650yds.    Personally I don’t want more than that much elevation for a 30-38 caliber.   I’ve hit at a 1000 with a 38-55 but I lost track of how many misses.

I have two MVA Soule and a Baldwin I’m considering trading staffs for their shorter #104 version to put on some smaller caliber Marlins.   But then-again, my eyes are shot so not shooting long range any longer.

For a CPA chambered in .38-55, the normal shooting distance is 200-yards. The farthest distance on a few occasions would a max of 500-meters (554-yards). Maybe 1400 fps mv, 345-grain bullet. Which MVA rear sight would be suggested? I’ll need a base compatible with the CPA tang mounting area.

Tom