tire size change up question...

I have worn out my 9x30 M/T radial drags, and thus need new slicks this season. Now, with my convertor change, I picked up in the 60' only to find the car not pulling as well down track. Where I used to run 118-119 @ 7100, the car now runs 116-117 @ 6700, so switching to a 28" tire looks to make sense. Are 10" wheels and 9x28 tires (vs 9x30) a workable package? The other change I'd like to make this year is a rear shock upgrade. The car has a 4-link/floater held up by stock 6-cyl leafs. Any shock recommendations?
link to half-decent launch vid-
http://www.youtube.com/watch?v=TNtkeUzzC9Q

I have ran ten inch wide rims using nine inch wide tires on my M.W. stocker years ago Some of the racers used 12 inch wide rims on thier nine inch wide tires I'm suprised the 30 inch tires slowed your car down

Actually, Cab, I've been running the 9x30 on 10" from the get-go. Where things have changed is the new convertor leaves a solid .05 better in the 60', but is slower from the 330 on. It appears that it locks up tighter than the old convertor did, and my little torque-challenged 360 just can't pull as hard because of it. Given that, as these tires are plumb wore out I'm thinking that going to a 28" tire would help give me more effective gear for the entire length of the track. I wasn't sure that 10's work with 9x28's, but if there are people running 12's on 9x30's I should be okay. The old convertor was a TCS 4-4200, the new one has about 500 rpm more stall. The change on the launch was like night and day, but it sure slowed the car down, overall.

You'll be fine, Lots of guys run a wider wheel, it helps stiffen the sidewall up substantially and allows the tire to work. Is your rear end moved backwards or are your wheel openings altered?

I had the same question last winter when I was building my new car. I have always run a 29.5X9 slick. With my new car weighing in almost 1,000 lbs. lighter than the truck I wanted to keep the same tire size just wider because I didn't want to get into the problem of too much tire for not enough motor. When choosing tire and rim size you must be careful no to go too wide on the rim or you will stretch the contact patch out and cause the tire to cup in the center loosing grip as the tire grows under acceleration. This goes the same for a rim that is too narrow.

The housing is in the stock place. I've "massaged" the wheel openings. I'd post a side pic but our main computer is fritzy and it has all the pics on it.