If you're after a 70's celica you have a choice of a TA22 or an RA23/RA28. The main difference between the two types is engine size; and in the case of the RA23 and RA28, the 23 is a coupe and the 28 is a hatch. The TA22 has a 1.6l engine and the RA23/28 has a 2.0l engine. Both are great cars and both can be hard to find parts for. A twin cam engine upgrade for both these cars will cost you about $1400-1600 (for a halfcut). These won't be reconditioned though. Having done some research into reconditioning for my Celica a reconditioned 18R motor (standard in the RA23/28) would cost me about $1200. This is probably the same for the 2T motor in the TA22.
Both these motors are very tough and reliable. So when you're shopping around try and find the car in the best condition you can and if possible try and find one with a 2TG or 18RG motor as these will be twin cam motors and a hell of a lot more power than the factory motors.
hope that gives you a bit more info to get you started. PM me if you have any more questions. happy to help.