My son purchased a 1983 GSL that needs replacement shocks on all 4 corners. I'd like go get something that is better handling than factory. I was looking at Tokico but I can't find any in stock that fit his car.

Also, I saw a set of four Tokico HP series that looked like complete "shock", not just the piston. What's the difference there? Can he just insert a replacement piston without the need for the end cap pieces usually found on shocks?

As you can tell, I'm no mechanic! Any suggestions appreciated.

 

First gens have a combination of shocks and struts ( shocks in the rear, struts in the front). shocks and struts perform near identical functions yet they can not be interchanged. A strut is a structural component of your cars suspension, a shock is not. That being said you're in luck as racing beat carries great shocks and struts

KONI Strut - Front for 81-85 RX-7 - Racing Beat

Koni front struts , the best you can get .

Tokico HP Shock Absorber for RX-7 Rear 79-85 - Racing Beat

Rear Tokico shocks


As to the question of replacing just the shock without the coil. You CAN but you have to remove the end caps. They sell a tool you WILL NEED to be called a coil compressor, it's a clamp that compresses the coil so you can remove the shock in the rear. DO NOT attempt to remove anything without first jacking the car up on stands and compressing the coils SECURELY. At the very least they can hurt you, at the worst kill you!

Strut Coil Spring Compressor Tool Suspension Auto Hydraulic Car Truck Repair | eBay

Heres a video explaining everything Its an easy DIY job. I changed them on my mustang .

 

Some thoughts on upgrading struts/shocks on 1st gens... our cars are 30+years old,the original springs are likely sagged from time(age) and the fact original spring metallurgy wasn't best quality so considering replacement springs as part of a shock upgrade would be advisable.
Original type(height)springs do best with an intermediate strut/shock such as KYB GR2 series.
Looking to further upgrade handling,changing spring rate/height is 1st thing to consider,then choose strut/shock combo to complement springs. The number of 1st gens left on road now almost relegate them to niche status and availability of choices for parts reflect that. There are a couple manufacturers of springs,Racing Beat has a good set i recommend for quality/consistency/price. Recommend Tokico Blue strut/shock combo with these springs as they complement them well. Tokico is original manufacturer of strut/shock combo that came on your car. Whatever choice you make for shocks,it's recommended that front/rear strut/shocks be of same manufacture so handling is balanced.
KYB strut/shocks look appealing because of their pricing,but upgraded springs will overpower them,several threads here you can search that document owners' findings after driving with them for awhile along with changes they made regarding shock choices after the fact.
Recommend shopping around for best prices on shocks when decision is made on what direction to go. Give some thought to replacing strut mounts/bearings-they basically carry the weight of front of car and they're same age as springs/shocks too. Kyb was the oe supplier for these and are still available.
Last thought: It's the same amount of labor to do any or all this work,as struts have to be disassembled to replace inserts. Springs,mounts can be installed on reassembly. Align car after driven a couple hundred miles to allow new springs time to settle.

 

I recall that I have heard that fox body mustang rear shocks fit the rears of the FB's. That may open up to Konis all around. Anyone able to confirm this?

 

It just says it again, if you do decide to install the spring yourself, do it SAFLEY. I just noticed you said it was your kid's car.
Jack stands and good quality coil compressors are a must. Don't cheap out .
I saw a guy under his car today without jack stands, just a jack , f***ing death wish right there.

 

Yes fox body Mustang shocks work on rears. I use the Koni Oranges with the RB springs. I fully agree with comment early about replacing the 30 year old springs. If you go with lower height springs; go with Tokico or Koni not KYB.

 

also 5" circle track springs fit the rear, lots of different height and stiffness options there. I am investigating whether SW20 MR2 struts fit the front with a few modifications. I know the AW11s fit so the SW20s should as well. I am looking into this because SW20 AGX struts are available, they are adjustable and should be similar to Illuminas at about half the price of the Konis.