Is Jupiter in the 8th similar to Jupiter in Scorpio?

Jupiter in 8th may be similar to Scorpio Jupiter as Scorpio and 8th house seem related. 

No.

Jupiter is part of our personality .. each planet is a specific inner need, and our behaviors arise from trying to meet our needs.

The SIGN a planet is in, is the general style of BEHAVIOR that we use in order to try to meet that need.

(All Signs have both positive and negative behaviors connected with that Sign, but how well/poorly we behave depends partly on how that planet "aspects" any of the other planets, and more importantly on how well we have matured and learned to work with our needs on a deliberate conscious level._

HOUSES are areas of life, so whatever House a planet is in, that is where the person looks to meet that need, in whatever style is indicated by the Sign that planet is in,

Jupiter in Scorpio is emotionally intense about networking. About whatever matters indicated by the House position of Jupiter.

Jupiter in the 8th tries to meet their netwoking needs through how they work with marriage expectations.  In whatever style of the Sign Jupiter is in.TT

Signs, Houses, and Planets are not interchangeable. Each is a different mechanism.

We say that Scorpio "rules" the 8th House because Scorpio is a style of emotional intensity, and the 8th Houe is about what we expect from our spouse and what they expect from us (and NOTHING hits us with more emotional intensity than this conflict between spouses).

And we say that Pluto "rules" Scorpio (and indirectly the 8th house too) because Pluto is our need to use our inner power. We either use it within ourselves to find the courage to change, transform, grow, or even just outlast a bad situation .. or we use it against others to try to make them change. Either direction requires intensity.

So the planet Pluto is about our need to use our intensity/power.

The Sign Scorpio is about BEING intense (any planet in Scorpio, Scorpio on any House)

The 8th House is about how we cope with the emotional intensity generated within a marriage.

No.  And Mars in Aries isn't liked Mars in the first house etc.

It makes enough sense to equate signs, houses and planets that it can help a beginner grasp some of the elements.  However, it has been taken too far when supposed practicing astrologers teach and believe it. This so called "astrological alphabet" is best ignored rather than learn and unlearn it. 

What Jupiter signifies in the 8th house depends a lot on what sign it is in, what houses it rules etc. If you learn nothing else, learn this: there is no one size fits all in astrology.  Jupiter in the 8th doesn't mean the same thing for everyone.  It could mean anything from a wealthy wife to a death from cancer. It depends on the rest of the chart. 

How about Uranus though.

I'd prefer to be in Wrigley Field in the 8th inning.  Astrology is bunk.