oiling issues

hi guys. The previous owner on my valiant used "76" 20W-50 racing motoroil, and the pressure is steady just under 75 psi (hv-pump). But when i went to the local shop to buy oil, he said that 75 psi is way to much and that the timing chain would wear down and lose its tension wery quickly. he recomended a 10w-30 and the pressure should never be higher then 50 psi.
what is your opinion about this?