Just got a 78 for 3,500 L48/both sets of t-tops 90k body and interior is great shape..the frame is of course gumby Anyway had it flat bedded over after 8 years of sitting inside and out.
Drained tank tossed on edelbrock, tune up etc, guess the guy gave up on it due to his timing was so far off, fired up...lumpy cam-motor/heads had some work done to it because I managed to pull a nice holeshot that could not come from a 180 hp.
Got the Lslip option so thats a start but anyway before I do a frame off this winter IM trying to beat off the struts so i can put my new ones on so I can at least drive it 2 more months, poor thing looks like its squating to go #2...hmmm after 30 years I think the shockmount has melded to the support. After trying to gently press it out then some gorilla tork then the old Heat N Beat was put to it..still nothing
Anyone know of any secret words to make it comply?..ive tried pocus cadabra but that just drove me more batty...i just joined this forum couple days ago, 2nd owned vette

 

First of all, your problem may not be the struts - it is more likely a combination of bushings and a sagging spring. But, to answer your question:

I had this same problem a few weeks ago on my 70... what I ended up doing was using an angle grinder (I used a 4"x1/8" thick whizz wheel, but larger diameter would be better) to carefully cut through the shock mount on either side of the strut rod, inside of the mounting brackets. This, then, allowed me to yank the strut rod out and use a c-clamp and a socket to press each remaining side of the shock mount from the trailing arm bracket.

Remember - HEAT IS YOUR FRIEND!!! And so is PB Blaster, for that matter.

Make sure that you have it unbolted/free from the bracket under the diff first - this will eliminate unnecessary complications and steresses.

I have heard of guys on this forum using a three-jaw gear puller to press the shock mount out by hookng the jaws on the opposing side bracket and putting the center pin on the shock mount and pressing.

One last thing - even though you're surely to be tempted, don't use a pipe wrench to try to turn the shock mount if it's frozen in place - it's got a flat portion to locate it and you'll end up cracking the trailing arm mounting bracket (thus require welding)... don't ask me how I know this...