Need help with AFR 165 heads

Hello,was wondering if any of you guys could point me in the right direction.I decided that i want a set of AFR 165 58cc heads for my 90 mustang.Alot of things about the motor i dont know,like the cam size or if its been bored or stroked.Should i pull the iron heads and take the car in to have them determine what cam,pistons and stroke i have before i order my heads? I dont want to order the heads only to find out i have clearance issues or if its stroked maybe the 185's would be better.Ive never built a motor but i am mechanicaly inclined and can do most work myself,so would this be easy to check myself without any special tools?I know i have crower enduro roller rockers and thats about it.lol Any help is appreciated!!

Its a street/strip car that id like to get into the 12's with.Im having it dyno'd and tuned after i do the heads.Right now it runs good,just looking for more power.Here is whts been done so far:

88 mustang gt
Mass air conversion
Trickflow intake
70mm bbk throttle body
bbk cold air intake
24# injectors
190lph pump
bbk fuel pressure reg
bbk equal length headers
bbk h pipe to flowmasters
msd 6al
bbk underdrive pullies
msd coil
Cobra computer,cobra mass air meter
ford racing aluminum driveshaft
tremec 3550hd trans,hurst shifter
Centerforce dual friction clutch
3:73 gears
Stock suspension,stock rims and tires
Not sure on what cam is in it but it has a lumpy idle
Dont know if its been bored out or stroked
Stock appearing heads,cant find any numbers on them
Pulled the valve cover and i see crowler enduro roller rockers,isky pushrod guides and look to be aftermarket pushrods

I just heard alot of good things about the afr 165 head(high velocity) but i'll have to check out the trickflow 170.To check ptv all i do is put clay in the valve relief and turn the motor over,measure thickness of imprint left in clay? What kind of clearance do i need?