How to get rid of understeer in a 1970 340

All the bushings were changed last year ,used polygraphite all around . Will look into the Hellwing . I beat the new crap boxes yes , but when I push it I get understeer , not when braking into turns but when accelerating into long sweepers or accelerating out of the turn . Feels like the front wheels are lifting and the car is not responding to the steering .
KYB had those on my ramcharger in the 70's , those ride hard real hard. What about Koni , they still around , worked well back in the day , will also look into bilstein . Have a feeling the KYB will rattle my teeth , a least that's what I remember in the ramcharger , up here with the potholes and rough roads they might break the car .

On long fast sweepers you don't exactly want the rear end fishtailing though. I can show you a video example of why.

hmmmmm..

Wonder if this is more of a floaty-loose kind of feeling as opposed to the front tires skidding outward.

What are your alignment specs?

How tight is your steering box?