There are methods to get approximate measurements for your sit bones (or whatever the proper terminology is). Basically sit on a stack of newspapers with a wet behind, then stand up and measure where the rough centers of the two main indentations are. This is what you want supported by your saddle.
Some saddles are wider, some have longer noses, some have different contours, any of which will affect comfort. If you know what your comfortable bike had for a saddle then you could find something similar.
As to the suspension seatpost, if I get a bike with one of those on it I usually swap it out for a non-susp. post. Too much bounce. Even on the MTB I've got set up as a commuter and grocery getter I've got a rigid seatpost. And on that bike I changed the stems and handlebars at least a dozen times with various combinations of bar/stem/shifters until I got it dialed in to where I find it comfortable. It currently has Serfas Drifter tires on it (26x1.25" road tread) but I'll be putting some 26x1.5" road tires on it this season to better handle softer/rougher roads. Going to use it as a fishing bike.
Last edited by treebound; 03-30-11 at 07:47 AM.