Ask Lemmygrad

Agreed, at the minimum one could at least bring as much knowledge (books, etc) regarding future sciences, technology and industry, agriculture, weaponry, medicines, the history as it's to come to pass, etc. along.

I'd also bring as much documentation as possible of how the Soviets fell (were betrayed from within), and how the Chinese model has succeeded especially since Deng and now with Xi- I'd bring as much information also, about the emergence of BRICS. I'd do my best to convince them to expand the Soviet model of development (which hopefully would adopt many aspects of the Chinese), to expand that prosperity and cooperation with not only the rest of the Warsaw pact (ideally I'd travel before WW2, that said) but to communist and trustworthy anti-imperialist states in the global south- ideally starting with Eurasia as the most "secure" continent to do so. (Personally I'd be hoping that a sort of "comintern/warsaw pact+ASEAN or SCO/if we're really optimistic, a sort of "greater Soviet federation" would emerge- spanning not just Russia and eastern/central Europe, but China, India, Iran and Afghanistan, the Turks if they could be brought into the fold, from there the Arab world and southeast Asia, eventually down into Africa and Latin America- basically, a generally contiguous, defensible, and ever-expanding union of Soviets, ideally with ever-increasing integration and cooperation, intense focus on development, exponential growth through scale).

And I'd bring whatever actual technology was possible, over as well. The current technology ubiquitous in daily life (computers, phones, routers, even- hell, even game consoles or TVs, speakers, etc. to ideally provide a glimpse of what Soviet soft power could be like and the technologies/ecosystems necessary to conquer the hearts and minds of the world with it. A generator as well (presumably one would hope that it could be reverse engineered), solar panels and batteries, information on radar systems, and whatever older tech I could get my hands on that were building blocks that brought our society to where it is now- calculators, pagers, older TVs/radios and other such electronics, DVDs, cassettes, floppy discs, older cameras (digital and pre-digital), maybe even some older punchcard system if I could get my hands on it, you name it.

It would naturally take a long while to reverse engineer and bring to production- but whatever can be carried over, by all means I'd do so.

Go back far enough (pre-WW2) and I think there's a possible chance that by this point in time (2020s) in the changed history, that a global, or at least Eurasian, Soviet/Comintern will have emerged.