Make it stop first, then handle second as mentioned.

Then "boost" is the way for budget hp.

A15 with single mazda rx7 series 4/5 turbo or cheap to25 or to3, water injection and a single 2 or 2.1/4 inch SU. (later can go straight gas and intercooler)
Inlet manifold mods and exhaust manifold should set you back 500-600 dollars turbo 250 and su $100. Water injection should be cheap if you make your own and decomping the a15 can be done with an open chamber head or custom decompression plate with custom copper gaskets which can be reused.
for under 1.5k you should have a the double the torque of an a15 if you assemble it yourself.