Ron got the axle, so here's a primer on tire size.
"P225/70R15" =
225 millimeter tread width, or divide by 25.4 to get 8.858...." etc. inches wide on the tread, or pretty close (there is some tolerance).
"/70" means side wall is 70% of tread width, or about 6.2 inches.
"R15" is rim diameter in inches, 15 inches.
So total tire height is 15 + 6.2 + 6.2, or a little over 27 inches tall.
BUT.... it will somewhat depend on tire inflation pressure, and how much weight is on it, because tires 'squish' down a little under load.
Anyway - bigger tires - a common size is 235/75R15, about 29 inches tall. Note they are '75' not '70' which means taller sidewall, better for running off road as there is more sidewall to give.
There are also old-style "inch" tires for off-roading, say 30x9.5 which is about 30 inches tall, and 9.5 inches wide (no matter the rim size but lots of them are on 15" rims).
So, personal opinion, going from say a 27" tire to a 29" tire won't be too noticeable in terms of robbing performance, but if you go crazy and want to run 31s or 33s, then yeah best budget in some $$ for a gearing swap to 4.10s, as well as speedometer correction.
I went from roughly 26" tires on my 97 to roughly 29" and it was fine, but my truck was purchased with a towing package, which gave it lower axle gears (3.55 vs. 3.27) but also I've got a 4.0 engine which has more torque, so I never had any issue with performance (well as much performance as one gets out of a 4.0 OHV engine, anyway).
I doubt you'd have to have a lift for 235/75 r15s. Might even be able to cram in 30x9.50s (I had them once, came with the wheels I bought) and they worked OK, although got a bit of rubbing on the sway bar at full turn).