Here’s the rules I used:
For every 10MR, the monster has one level. If MR is halfway or more to the next level (15, 25, 35, etc) or more, then add +1 to HP but not exceeding 3. So basically the minimum HP is higher.
Level 1 saving rolls correspond to a standard P&P save. For each level over 1, apply a -1 penalty to the dice roll. If the character has the applicable stat for the SR, add +1 to the dice roll.
For fixed number saving rolls, round them to the nearest saving roll level. For example, there’s one scene where you add your Luck to your Charisma, and then roll dice to get 36 or higher. 35 is a 4th level saving roll, so roll a -4.
So on with the famous (or infamous) Buffalo Castle:
First contestant is Thrag the Dwarf. Constitution. Hand ax, chain, shield. All room in Buffalo castle are lit, so did not buy any torches. He meets a troll sitting atop a treasure chest. Thrag tries to negotiate with the troll, fails, and the troll attacks. Level 4 troll, 10 hp, +1 to hit, +1 damage. The two combatants trade blows until Thrag is worn out. He tries to flee, but the troll blocks off the exit and crushes him.
The second contestant, Biff the Wise human warrior, sees that Thrag did not return, so enters the castle through a different door. He brings a battle ax and chain armor. He enters a magical portal and ends up in a room full of gold coins. He collects 60 gp before two swarms of killer bees show up. He gets stung a couple times but splats them all with the flat side of his ax. Leaving, he encounters a room with a giant swinging pendulum. He bolts past it without getting hurt, and soon meets a wandering giant. Giant, Level 8, 18 HP, +2 hit, +2 damage. Biff decides discretion is the better part of valor, and decides to flee. Four killer bees block the exit. It’s a rough fight but Biff wins his way through, and escapes.
What will Biff do now? I will find out next time I play.
I think I got the monster conversions and saving rolls correct. There is no Wisdom stat in Tunnels & Trolls. Instead there is a Luck stat. Therefore, for now I think one should use Luck in place of Wisdom. This makes sense, because solos are often dependent on Luck SRs unless specified otherwise. I’ll try it next time.