A Mid-Range 1.25m Engine?

[MarcRan17]

I think there's a serious gap between efficient engines and powerful ones for 1.25m parts (Stock/Stockalike that is). Example A: The LV-T30 and the LV-T45 both have appx. 200kN thrust, and 370s Vac ISP, but the next level down is the LV-909 with 50kN thrust and 390 Vac ISP. There's nothing good in between. I'd love it if there was an engine That had say 100-150kN thrust, and say 375-380s Vac ISP. It'd be perfect for Spaceplanes, where the Weight of the LVT's renders their extra thrust useless, and the low thrust of the 909 makes it too weak. Can anyone point me to this mod if it already exists? Otherwise I'd love to see it made!

I should note that I know the Aerospike fits this description perfectly, but You unlock that quite late in the tech tree, and it requires the final Research center upgrade. In addition, the requested part wouldn't make the aerospike obselete, as the aerospike still boasts it's universal ISP

[Streetwind]

KW Rocketry has a 0.75t, 90 kN, 400 Isp engine. You might say "that's not between 370 and 390", but it actually does have slightly less dV than the LV-909 due to the weight difference. Still more dV than using a LV-T30 though. So effectively it results in what you're looking for.

[Rarity]

aren't aerospikes fairly heavy, too?