Almost every old rifle I own has the shorter 7.2" spacing done on them. Never saw a reason to go to 10.3", but if you're shooting 300 yds. or less it will give finer adjustments.

Schuetzendave and marlinguy thanks for your interest in my dilemma.   
Even though I will probably never shoot at 1000 yd targets I now understand scope placement implications. 

Oldbee, you lose elevation adjustment the wider the distance between scope blocks.  If you look at Schuetzendave's little chart carefully, you will notice that you lose almost 30% if you use the wide spacing,  Here is a link to something I did in the past and it worked quite well. 

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I have since abandoned this and have gone to the tall DZ Arms mounts.  Not because the earlier system didn't work but because it was too hard to read the lines on the Unertl scale in bright sunlight.  DZ Arms alters the spacing, also, white on black is easier for me to read.