John has it almost 100% correct. The only thing he was incorrect about was that the L-88 wasn't installed by Lenco (the transmission/driveline company), but was installed by Chevrolet dealers such as Yenko (probably who you were thinking about), Dick Harrell and Baldwin-Motion.
Yenko also installed them in Novas, in addition to the others John mentioned. These vehicles prepared by Yenko often had special interiors also installed in them, and it was common to see "Y S C" embroidered on the headrests. YSC stands for "Yenko Super Car."
Now why can I remember this stuff, but I have no clue when my girlfriend's birthday is?
Had 1 in a 72 Jeep CJ-5 that raced at Tri- county 4x4 club back in 1975. Their was a guy that had a 426 hemi & another that had a 454 with nitro (back then you had a switch to turn on & off the gas, no computers just prayers) all in Jeeps.
I thought only the tri power 427 ,(L89?)in the vettes had the 435hp,and the all aluminum ZL1.I was pretty sure thr L88 was 425hp.I havent read any of my old mags,to keep fresh on this stuff,so im slipping a little,LOL.I used to know every RPO,for 99% of GM.s