Need help with a late 60's 20 cc I/O

[jkully]

I just picked up a late 60's (I think)20 cc with a 4cyl Merc I/O. and an external fuel tank. I have read most all of the post here and it's a great site, but I several questions on my refurb job ahead. 1. any one out there with a old 20 cc install a below deck tank? and Where did you place it(fore/aft/midship)? 2. Because of the tail weight of the boat with the I/O, would it be better to convert to an O/B configuration for 25" shaft and 130 to 150 O/B. The weight saving should be around 200 lbs. Would like to hear feed back from anyone with any suggestions.

PS. I love the 4cyl I/O, but could use the space better.