the ideal ratio varies as stated, but you can be scientific in your search. tire size (245/60 r15 (26.6") what i used to run) will change your ratio. even switching from 245/60 to 245/65 R15 (27.5") will change your readings. itll give you more top end and less acceleration (even if it IS just a small ammount) and your speedometer will say you are doing 60 when you are actually doing 65 or so. smaller tires will show you are going faster than than you are. there is a nice chart to figure out tire size vs ratio (i use this alot when deciding gears in 4x4's). http://www.4lo.com/calc/geartable.htm it shows tire size vs gears to give desired rpm. there is a red/green/yellow reading for mileage or power or rpm desired. you want it geared for more power, use tire diameter shown and and you can target a certain range. the chart starts at 27" tho. it will give you a good idea of how it all works. http://www.4lo.com/ this is the home page of the guy where he has several charts. one will help figure out your speedometer reading now vs before you changed tires. i would say look at the first page and find you gear ratio. then scroll down and look at desired rpm (at a set 65 mph). follow it to the tire size. easy chart, but look around at the different sizes close to your ideal numbers. you might find something that will fit under the rear fenders and still hook you up. also, you can find the gear and the tire size that you HAD, then find your rpm range at 65. now try to match new tires to that. if you do get a match, your speedometer will read correctly. basically, you go bigger tires which raises your overall gear ratio, then lower your gears to bring your overall ratio back down. its one giant "over all" gear ratio which includes tranny, transfer case (if you had a 4x4 or all wheel drive), differential AND tire size. if you have an OD, then use the 1:1 gear (usually 4th in a 5 speed, or 3rd in auto OD). http://www.4lo.com/calc/gearmetric.htm use this to find tire size in inches vs metric. make sure you clear the diameter field everytime you change something or it wont display correctly. hope this sheds some light on the subject and helps you newer guys out..=) also, check his home page for other charts/calculators. he has a hp chart, BAC..other stuff.
28x9x15 slicks are a good combo on 8 or 9in wheels. Depends on engine mod's and 1/8th or 1/4mile track. Had 4:11's in the Mav when first built with mild 302. Stock converter and c4 it was a dog in the 1/8th and 1000ft. Higher stall and 4.62 made a big difference, cam spec's and such will also affect the outcome.
