Wow! Thank you all for the input. Based on your suggestions/experience and from what I've read on other forums, I have the following choices:
A) Flat towing the RX7 behind the Volvo V70 estate:
1) I will have to fit the correct rated hitch on the Volvo (which I would have to do regardless) - approx cost around 300 - 400 bucks including the electrical connections.
2) I will have to purchase and modify a tow bar (minimum 3,000 lb rating) and install the fittings on the RX7 steel bumper (1979 bumper).
3) The towed vehicle must be plated per Illinois law which isn't a problem since I already have it titled and plated and have been driving it on the street. I also don't need the brakes on the towed vehicle to activate.
4) I can actually optimize the suspension for the track which will be a considerable improvement over the compromise setup I have right now (high ride height and soft shocks to deal with the extra weight of loaded track equipment). I already have two sets of wheels with tires that I change out depending on the conditions. One set has Toyo R888R which I use to drive to and from the track and on the track when it's raining. The other set has Toyo RR which I used solely on the track when dry. I also have another set of steel Diamond wheels with some very tired Toyo RA1 which can be sacrificial tow tires. The Volvo has enough room for two sets plus gear.
5) The tow bar is easy to store when not in use. I don't have a garage since I live at an apartment complex. I keep and work on the race car in my half of my fiance's two car garage so I don't have any room for a trailer or a dolly.
6) If the race car suffers severe enough damage, I can drive over to the local U-Haul when they open and one-way rent a four wheel trailer and trailer the car home. Of course, it will probably overload the Volvo but in an emergency, it will have to do.
B) Renting a U-Haul dolly and towing it with the Volvo V70 estate:
1) See A1
2) I will have to rent a U-Haul dolly (cheap). I can easily disconnect the driveshaft at the junction of the rear differential (two flanges that mate and four bolts that hold the flanges together) and strap the unconnected end of the driveshaft up against the chassis. I probably won't need to seal up the transmission output end since the driveshaft is still in place. I've also read of RX7 racers simply overfilling the gearbox in order to keep the input bearing alive. But I'm still on the fence.
3) A3 still applies because two wheels are on the ground.
4) Same as A4 except I can't set up the suspension too low otherwise the rear will scrape.
5) The dolly would have to be rented since I absolutely have no room to store it nor the finances to rent a storage space for it. As it is, my fiance has been more than generous in putting up with the tools and spares crowding the garage and the occasional dinning table of carb rebuild and parts. I doubt that she would take kindly to a tow dolly sitting idle on her driveway or her lawn.
6) See A6 above except I can simply trade the rented dolly for a four wheeled trailer.
I think I need to do more researching and listening to more advice.