[swordtart]

If you use the Duel Track version of the 150 cid plant and omit the ramplate the numbers are as written for weight and cost.

The design is a space under max. The duel track plant takes up 1 more space than the current version. The old plant is 125lb lighter.

The armour summary indicates ramplate, but the description says nothing about it (and a ramplate on a compact is a silly idea).

The 1/3 space violation however is insurmountable (and the HC should be 3 not 2).

Considering 43's design, I'd suggest a few amendments.
Lose the ramplate as I think it is a typo.
Replace Heavy chassis with Extra Heavy as suggested.
Drop Suspension to Improved to match the stated HC 2.
Replace the BC with ATG and HEAT as suggested.
Fit a HRSWC to restore the to hit number of 6.
Swap 5 points of front armour from plastic to metal.
Leave the duelling tank. You need all the help you can get.

That leaves you $672, 25lb and 2 spaces for personal kit or component armour etc.

You could spend $600 on upgrading the carb, but it only gets you an extra 5 mph top speed.